diff --git a/nightlight/crates/nightlight-server/src/config.rs b/nightlight/crates/nightlight-server/src/config.rs
index 4626695..dd2300b 100644
--- a/nightlight/crates/nightlight-server/src/config.rs
+++ b/nightlight/crates/nightlight-server/src/config.rs
@@ -129,17 +129,6 @@ impl Config {
         Ok(config)
     }
 
-    /// Load configuration from file, or use defaults if file doesn't exist
-    pub fn load_or_default() -> Result<Self> {
-        match Self::from_file("config.yaml") {
-            Ok(config) => Ok(config),
-            Err(_) => {
-                tracing::warn!("No config file found, using defaults");
-                Ok(Self::default())
-            }
-        }
-    }
-
     /// Save configuration to a YAML file
     pub fn save(&self, path: &str) -> Result<()> {
         let content = serde_yaml::to_string(self)?;
diff --git a/nightlight/crates/nightlight-server/src/grpc.rs b/nightlight/crates/nightlight-server/src/grpc.rs
new file mode 100644
index 0000000..5cee297
--- /dev/null
+++ b/nightlight/crates/nightlight-server/src/grpc.rs
@@ -0,0 +1,502 @@
+use std::sync::Arc;
+use std::time::Instant;
+
+use chrono::Utc;
+use tonic::{Request, Response, Status};
+
+use crate::ingestion::IngestionMetrics;
+use crate::query::{QueryMetrics, QueryResult as InstantQueryData, QueryService, RangeQueryResult};
+use crate::storage::{Storage, StorageStats};
+use nightlight_api::nightlight::admin_server::Admin;
+use nightlight_api::nightlight::metric_query_server::MetricQuery;
+use nightlight_api::nightlight::{
+    BuildInfoRequest, BuildInfoResponse, ComponentHealth, HealthRequest, HealthResponse,
+    LabelValuesRequest, LabelValuesResponse, QueryData, QueryResponse, QueryResult, SamplePair,
+    SeriesLabels, SeriesQueryRequest, SeriesQueryResponse, StatsRequest, StatsResponse,
+};
+use nightlight_types::Error;
+
+#[derive(Clone)]
+pub struct MetricQueryServiceImpl {
+    query: QueryService,
+}
+
+#[derive(Clone)]
+pub struct AdminServiceImpl {
+    storage: Arc<Storage>,
+    ingestion_metrics: Arc<IngestionMetrics>,
+    query_metrics: Arc<QueryMetrics>,
+    started_at: Instant,
+}
+
+impl MetricQueryServiceImpl {
+    pub fn new(query: QueryService) -> Self {
+        Self { query }
+    }
+}
+
+impl AdminServiceImpl {
+    pub fn new(
+        storage: Arc<Storage>,
+        ingestion_metrics: Arc<IngestionMetrics>,
+        query_metrics: Arc<QueryMetrics>,
+    ) -> Self {
+        Self {
+            storage,
+            ingestion_metrics,
+            query_metrics,
+            started_at: Instant::now(),
+        }
+    }
+}
+
+#[tonic::async_trait]
+impl MetricQuery for MetricQueryServiceImpl {
+    async fn instant_query(
+        &self,
+        request: Request<nightlight_api::nightlight::InstantQueryRequest>,
+    ) -> Result<Response<QueryResponse>, Status> {
+        let request = request.into_inner();
+        let time = if request.time == 0 {
+            Utc::now().timestamp_millis()
+        } else {
+            request.time
+        };
+
+        let response = match self.query.execute_instant_query(&request.query, time).await {
+            Ok(result) => QueryResponse {
+                status: "success".to_string(),
+                data: Some(instant_query_data_to_proto(result)),
+                error: String::new(),
+                error_type: String::new(),
+                warnings: Vec::new(),
+            },
+            Err(error) => QueryResponse {
+                status: "error".to_string(),
+                data: None,
+                error: error.to_string(),
+                error_type: query_error_type(&error).to_string(),
+                warnings: Vec::new(),
+            },
+        };
+
+        Ok(Response::new(response))
+    }
+
+    async fn range_query(
+        &self,
+        request: Request<nightlight_api::nightlight::RangeQueryRequest>,
+    ) -> Result<Response<QueryResponse>, Status> {
+        let request = request.into_inner();
+
+        let response = match self
+            .query
+            .execute_range_query(&request.query, request.start, request.end, request.step)
+            .await
+        {
+            Ok(result) => QueryResponse {
+                status: "success".to_string(),
+                data: Some(range_query_data_to_proto(result)),
+                error: String::new(),
+                error_type: String::new(),
+                warnings: Vec::new(),
+            },
+            Err(error) => QueryResponse {
+                status: "error".to_string(),
+                data: None,
+                error: error.to_string(),
+                error_type: query_error_type(&error).to_string(),
+                warnings: Vec::new(),
+            },
+        };
+
+        Ok(Response::new(response))
+    }
+
+    async fn series_query(
+        &self,
+        request: Request<SeriesQueryRequest>,
+    ) -> Result<Response<SeriesQueryResponse>, Status> {
+        let request = request.into_inner();
+        let response = match self
+            .query
+            .series_metadata(
+                &request.r#match,
+                optional_millis(request.start),
+                optional_millis(request.end),
+            )
+            .await
+        {
+            Ok(series) => SeriesQueryResponse {
+                status: "success".to_string(),
+                data: series
+                    .into_iter()
+                    .map(|labels| SeriesLabels { labels })
+                    .collect(),
+                error: String::new(),
+            },
+            Err(error) => SeriesQueryResponse {
+                status: "error".to_string(),
+                data: Vec::new(),
+                error: error.to_string(),
+            },
+        };
+
+        Ok(Response::new(response))
+    }
+
+    async fn label_values_query(
+        &self,
+        request: Request<LabelValuesRequest>,
+    ) -> Result<Response<LabelValuesResponse>, Status> {
+        let request = request.into_inner();
+        let response = match self
+            .query
+            .label_values_for_matchers(
+                &request.label_name,
+                &request.r#match,
+                optional_millis(request.start),
+                optional_millis(request.end),
+            )
+            .await
+        {
+            Ok(values) => LabelValuesResponse {
+                status: "success".to_string(),
+                data: values,
+                error: String::new(),
+            },
+            Err(error) => LabelValuesResponse {
+                status: "error".to_string(),
+                data: Vec::new(),
+                error: error.to_string(),
+            },
+        };
+
+        Ok(Response::new(response))
+    }
+}
+
+#[tonic::async_trait]
+impl Admin for AdminServiceImpl {
+    async fn health(
+        &self,
+        _request: Request<HealthRequest>,
+    ) -> Result<Response<HealthResponse>, Status> {
+        let storage_result = self.storage.stats().await;
+        let status = if storage_result.is_ok() { "ok" } else { "degraded" };
+        let storage_message = match &storage_result {
+            Ok(_) => "storage ready".to_string(),
+            Err(error) => error.to_string(),
+        };
+
+        Ok(Response::new(HealthResponse {
+            status: status.to_string(),
+            message: "nightlight ready".to_string(),
+            components: vec![
+                ComponentHealth {
+                    name: "storage".to_string(),
+                    status: status.to_string(),
+                    message: storage_message,
+                },
+                ComponentHealth {
+                    name: "ingestion".to_string(),
+                    status: "ok".to_string(),
+                    message: "remote_write endpoint ready".to_string(),
+                },
+                ComponentHealth {
+                    name: "query_engine".to_string(),
+                    status: "ok".to_string(),
+                    message: "http and grpc query paths ready".to_string(),
+                },
+            ],
+        }))
+    }
+
+    async fn stats(
+        &self,
+        _request: Request<StatsRequest>,
+    ) -> Result<Response<StatsResponse>, Status> {
+        let storage = self
+            .storage
+            .stats()
+            .await
+            .map_err(|error| Status::internal(error.to_string()))?;
+        let ingestion = self.ingestion_metrics.snapshot();
+        let query = self.query_metrics.snapshot();
+
+        Ok(Response::new(StatsResponse {
+            storage: Some(storage_stats_to_proto(storage)),
+            ingestion: Some(nightlight_api::nightlight::IngestionStats {
+                samples_ingested_total: ingestion.samples_ingested_total,
+                write_requests_total: ingestion.write_requests_total,
+                write_requests_failed: ingestion.write_requests_failed,
+                samples_per_second: ingestion.samples_per_second,
+                buffer_samples: ingestion.buffer_samples,
+            }),
+            query: Some(nightlight_api::nightlight::QueryStats {
+                queries_total: query.queries_total,
+                queries_failed: query.queries_failed,
+                queries_active: query.queries_active,
+                query_duration_p50: query.query_duration_p50,
+                query_duration_p95: query.query_duration_p95,
+                query_duration_p99: query.query_duration_p99,
+            }),
+            uptime_seconds: self.started_at.elapsed().as_secs(),
+        }))
+    }
+
+    async fn build_info(
+        &self,
+        _request: Request<BuildInfoRequest>,
+    ) -> Result<Response<BuildInfoResponse>, Status> {
+        Ok(Response::new(BuildInfoResponse {
+            version: env!("CARGO_PKG_VERSION").to_string(),
+            commit: option_env!("GIT_COMMIT").unwrap_or("unknown").to_string(),
+            build_time: option_env!("BUILD_TIME").unwrap_or("unknown").to_string(),
+            rust_version: option_env!("RUSTC_VERSION").unwrap_or("unknown").to_string(),
+            target: format!("{}-{}", std::env::consts::ARCH, std::env::consts::OS),
+        }))
+    }
+}
+
+fn optional_millis(value: i64) -> Option<i64> {
+    if value == 0 {
+        None
+    } else {
+        Some(value)
+    }
+}
+
+fn query_error_type(error: &Error) -> &'static str {
+    match error {
+        Error::InvalidMetric(_) | Error::InvalidLabel(_) | Error::InvalidTimeRange(_) => "bad_data",
+        Error::Timeout(_) => "timeout",
+        _ => "execution",
+    }
+}
+
+fn instant_query_data_to_proto(result: InstantQueryData) -> QueryData {
+    QueryData {
+        result_type: result.result_type,
+        result: result
+            .result
+            .into_iter()
+            .map(|series| QueryResult {
+                metric: series.metric,
+                values: Vec::new(),
+                value: series.value.map(sample_pair_from_tuple),
+            })
+            .collect(),
+    }
+}
+
+fn range_query_data_to_proto(result: RangeQueryResult) -> QueryData {
+    QueryData {
+        result_type: result.result_type,
+        result: result
+            .result
+            .into_iter()
+            .map(|series| QueryResult {
+                metric: series.metric,
+                values: series
+                    .values
+                    .into_iter()
+                    .map(sample_pair_from_tuple)
+                    .collect(),
+                value: None,
+            })
+            .collect(),
+    }
+}
+
+fn sample_pair_from_tuple((timestamp, value): (i64, f64)) -> SamplePair {
+    SamplePair { timestamp, value }
+}
+
+fn storage_stats_to_proto(stats: StorageStats) -> nightlight_api::nightlight::StorageStats {
+    nightlight_api::nightlight::StorageStats {
+        active_series: stats.active_series,
+        total_samples: stats.total_samples,
+        blocks_count: stats.blocks_count,
+        head_samples: stats.head_samples,
+        disk_bytes_used: stats.disk_bytes_used,
+        oldest_sample_time: stats.oldest_sample_time,
+        newest_sample_time: stats.newest_sample_time,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::ingestion::IngestionService;
+    use crate::storage::Storage;
+    use nightlight_api::nightlight::{
+        InstantQueryRequest, LabelValuesRequest, SeriesQueryRequest,
+    };
+    use nightlight_api::prometheus::{Label, Sample, TimeSeries, WriteRequest};
+
+    #[tokio::test]
+    async fn instant_query_grpc_returns_metric_data() {
+        let dir = tempfile::tempdir().unwrap();
+        let storage = Arc::new(Storage::new(dir.path().to_str().unwrap()).unwrap());
+        let ingestion = IngestionService::new(Arc::clone(&storage));
+        ingestion
+            .process_write_request(WriteRequest {
+                timeseries: vec![TimeSeries {
+                    labels: vec![
+                        Label {
+                            name: "__name__".to_string(),
+                            value: "grpc_metric".to_string(),
+                        },
+                        Label {
+                            name: "job".to_string(),
+                            value: "nightlight".to_string(),
+                        },
+                    ],
+                    samples: vec![Sample {
+                        value: 12.5,
+                        timestamp: 1_000,
+                    }],
+                }],
+            })
+            .await
+            .unwrap();
+
+        let service = MetricQueryServiceImpl::new(QueryService::from_storage(storage.queryable()));
+        let response = service
+            .instant_query(Request::new(InstantQueryRequest {
+                query: "grpc_metric{job=\"nightlight\"}".to_string(),
+                time: 2_000,
+                timeout: 0,
+            }))
+            .await
+            .unwrap()
+            .into_inner();
+
+        assert_eq!(response.status, "success");
+        let data = response.data.unwrap();
+        assert_eq!(data.result.len(), 1);
+        assert_eq!(
+            data.result[0].metric.get("__name__").map(String::as_str),
+            Some("grpc_metric")
+        );
+        assert_eq!(data.result[0].value.as_ref().map(|value| value.value), Some(12.5));
+    }
+
+    #[tokio::test]
+    async fn metadata_queries_grpc_filter_series() {
+        let dir = tempfile::tempdir().unwrap();
+        let storage = Arc::new(Storage::new(dir.path().to_str().unwrap()).unwrap());
+        let ingestion = IngestionService::new(Arc::clone(&storage));
+        ingestion
+            .process_write_request(WriteRequest {
+                timeseries: vec![
+                    TimeSeries {
+                        labels: vec![
+                            Label {
+                                name: "__name__".to_string(),
+                                value: "grpc_metric".to_string(),
+                            },
+                            Label {
+                                name: "job".to_string(),
+                                value: "api".to_string(),
+                            },
+                        ],
+                        samples: vec![Sample {
+                            value: 1.0,
+                            timestamp: 1_000,
+                        }],
+                    },
+                    TimeSeries {
+                        labels: vec![
+                            Label {
+                                name: "__name__".to_string(),
+                                value: "grpc_metric".to_string(),
+                            },
+                            Label {
+                                name: "job".to_string(),
+                                value: "worker".to_string(),
+                            },
+                        ],
+                        samples: vec![Sample {
+                            value: 2.0,
+                            timestamp: 2_000,
+                        }],
+                    },
+                ],
+            })
+            .await
+            .unwrap();
+
+        let service = MetricQueryServiceImpl::new(QueryService::from_storage(storage.queryable()));
+        let series = service
+            .series_query(Request::new(SeriesQueryRequest {
+                r#match: vec!["job=api".to_string()],
+                start: 0,
+                end: 0,
+            }))
+            .await
+            .unwrap()
+            .into_inner();
+        assert_eq!(series.status, "success");
+        assert_eq!(series.data.len(), 1);
+
+        let label_values = service
+            .label_values_query(Request::new(LabelValuesRequest {
+                label_name: "job".to_string(),
+                r#match: vec!["__name__=grpc_metric".to_string()],
+                start: 0,
+                end: 0,
+            }))
+            .await
+            .unwrap()
+            .into_inner();
+        assert_eq!(label_values.status, "success");
+        assert_eq!(label_values.data, vec!["api".to_string(), "worker".to_string()]);
+    }
+
+    #[tokio::test]
+    async fn admin_stats_report_ingestion_and_query_counters() {
+        let dir = tempfile::tempdir().unwrap();
+        let storage = Arc::new(Storage::new(dir.path().to_str().unwrap()).unwrap());
+        let ingestion = IngestionService::new(Arc::clone(&storage));
+        ingestion
+            .process_write_request(WriteRequest {
+                timeseries: vec![TimeSeries {
+                    labels: vec![Label {
+                        name: "__name__".to_string(),
+                        value: "admin_metric".to_string(),
+                    }],
+                    samples: vec![Sample {
+                        value: 3.0,
+                        timestamp: 1_000,
+                    }],
+                }],
+            })
+            .await
+            .unwrap();
+
+        let query = QueryService::from_storage(storage.queryable());
+        query.execute_instant_query("admin_metric", 2_000).await.unwrap();
+
+        let admin = AdminServiceImpl::new(
+            Arc::clone(&storage),
+            ingestion.metrics(),
+            query.metrics(),
+        );
+        let stats = admin
+            .stats(Request::new(StatsRequest {}))
+            .await
+            .unwrap()
+            .into_inner();
+
+        assert_eq!(stats.storage.as_ref().map(|value| value.total_samples), Some(1));
+        assert_eq!(
+            stats.ingestion
+                .as_ref()
+                .map(|value| value.samples_ingested_total),
+            Some(1)
+        );
+        assert_eq!(stats.query.as_ref().map(|value| value.queries_total), Some(1));
+    }
+}
diff --git a/nightlight/crates/nightlight-server/src/ingestion.rs b/nightlight/crates/nightlight-server/src/ingestion.rs
index 54f6589..93cc8f7 100644
--- a/nightlight/crates/nightlight-server/src/ingestion.rs
+++ b/nightlight/crates/nightlight-server/src/ingestion.rs
@@ -16,10 +16,11 @@ use nightlight_types::Error;
 use prost::Message;
 use snap::raw::Decoder as SnappyDecoder;
 use std::sync::Arc;
-use tokio::sync::RwLock;
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::time::Instant;
 use tracing::{debug, error, info, warn};
 
-use crate::query::QueryableStorage;
+use crate::storage::Storage;
 
 /// Maximum write request size (10 MB uncompressed)
 const MAX_REQUEST_SIZE: usize = 10 * 1024 * 1024;
@@ -27,28 +28,33 @@ const MAX_REQUEST_SIZE: usize = 10 * 1024 * 1024;
 /// Ingestion service state
 #[derive(Clone)]
 pub struct IngestionService {
-    storage: Arc<RwLock<QueryableStorage>>,
+    storage: Arc<Storage>,
     metrics: Arc<IngestionMetrics>,
 }
 
-/// Ingestion metrics for monitoring
-struct IngestionMetrics {
-    samples_received: Arc<std::sync::atomic::AtomicU64>,
-    samples_invalid: Arc<std::sync::atomic::AtomicU64>,
-    requests_total: Arc<std::sync::atomic::AtomicU64>,
-    requests_failed: Arc<std::sync::atomic::AtomicU64>,
+#[derive(Debug)]
+pub struct IngestionMetrics {
+    samples_received: AtomicU64,
+    samples_invalid: AtomicU64,
+    requests_total: AtomicU64,
+    requests_failed: AtomicU64,
+    started_at: Instant,
+}
+
+#[derive(Debug, Clone, Copy, Default)]
+pub struct IngestionMetricsSnapshot {
+    pub samples_ingested_total: u64,
+    pub write_requests_total: u64,
+    pub write_requests_failed: u64,
+    pub samples_per_second: f64,
+    pub buffer_samples: u64,
 }
 
 impl IngestionService {
-    pub fn new(storage: Arc<RwLock<QueryableStorage>>) -> Self {
+    pub fn new(storage: Arc<Storage>) -> Self {
         Self {
             storage,
-            metrics: Arc::new(IngestionMetrics {
-                samples_received: Arc::new(std::sync::atomic::AtomicU64::new(0)),
-                samples_invalid: Arc::new(std::sync::atomic::AtomicU64::new(0)),
-                requests_total: Arc::new(std::sync::atomic::AtomicU64::new(0)),
-                requests_failed: Arc::new(std::sync::atomic::AtomicU64::new(0)),
-            }),
+            metrics: Arc::new(IngestionMetrics::new()),
         }
     }
 
@@ -59,10 +65,14 @@ impl IngestionService {
             .with_state(self)
     }
 
+    pub fn metrics(&self) -> Arc<IngestionMetrics> {
+        Arc::clone(&self.metrics)
+    }
+
     /// Process a WriteRequest and write to shared storage
-    async fn process_write_request(&self, request: WriteRequest) -> Result<u64, Error> {
-        let mut storage = self.storage.write().await;
+    pub(crate) async fn process_write_request(&self, request: WriteRequest) -> Result<u64, Error> {
         let mut samples_processed = 0;
+        let mut series_to_append = Vec::new();
 
         for ts in request.timeseries {
             // Validate and normalize labels
@@ -83,7 +93,7 @@ impl IngestionService {
                 // Validate sample
                 if !sample.value.is_finite() {
                     warn!("Invalid sample value: {}", sample.value);
-                    self.metrics.samples_invalid.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
+                    self.metrics.samples_invalid.fetch_add(1, Ordering::Relaxed);
                     continue;
                 }
 
@@ -113,20 +123,56 @@ impl IngestionService {
                 samples: internal_samples,
             };
 
-            // Write to shared storage (upsert merges samples)
-            storage.upsert_series(time_series);
+            series_to_append.push(time_series);
         }
 
-        self.metrics.samples_received.fetch_add(samples_processed, std::sync::atomic::Ordering::Relaxed);
+        self.storage
+            .append(series_to_append)
+            .await
+            .map_err(|error| Error::Storage(error.to_string()))?;
+        self.metrics
+            .samples_received
+            .fetch_add(samples_processed, Ordering::Relaxed);
 
         Ok(samples_processed)
     }
 
     /// Get current storage statistics
-    pub async fn storage_stats(&self) -> (usize, usize) {
-        let storage = self.storage.read().await;
-        let total_samples: usize = storage.series.values().map(|s| s.samples.len()).sum();
-        (total_samples, storage.series.len())
+    pub async fn storage_stats(&self) -> Result<(usize, usize), Error> {
+        let stats = self
+            .storage
+            .stats()
+            .await
+            .map_err(|error| Error::Storage(error.to_string()))?;
+        Ok((stats.total_samples as usize, stats.active_series as usize))
+    }
+}
+
+impl IngestionMetrics {
+    fn new() -> Self {
+        Self {
+            samples_received: AtomicU64::new(0),
+            samples_invalid: AtomicU64::new(0),
+            requests_total: AtomicU64::new(0),
+            requests_failed: AtomicU64::new(0),
+            started_at: Instant::now(),
+        }
+    }
+
+    pub fn snapshot(&self) -> IngestionMetricsSnapshot {
+        let uptime = self.started_at.elapsed().as_secs_f64();
+        let samples_ingested_total = self.samples_received.load(Ordering::Relaxed);
+        IngestionMetricsSnapshot {
+            samples_ingested_total,
+            write_requests_total: self.requests_total.load(Ordering::Relaxed),
+            write_requests_failed: self.requests_failed.load(Ordering::Relaxed),
+            samples_per_second: if uptime > 0.0 {
+                samples_ingested_total as f64 / uptime
+            } else {
+                0.0
+            },
+            buffer_samples: 0,
+        }
     }
 }
 
@@ -135,7 +181,7 @@ async fn handle_remote_write(
     State(service): State<IngestionService>,
     body: Bytes,
 ) -> Response {
-    service.metrics.requests_total.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
+    service.metrics.requests_total.fetch_add(1, Ordering::Relaxed);
 
     debug!("Received remote_write request, size: {} bytes", body.len());
 
@@ -150,7 +196,7 @@ async fn handle_remote_write(
         Ok(data) => data,
         Err(e) => {
             error!("Snappy decompression failed: {}", e);
-            return IngestionError::DecompressionFailed(e.to_string()).into_response();
+            return IngestionError::DecompressionFailed.into_response();
         }
     };
 
@@ -161,7 +207,7 @@ async fn handle_remote_write(
         Ok(req) => req,
         Err(e) => {
             error!("Protobuf decode failed: {}", e);
-            return IngestionError::InvalidProtobuf(e.to_string()).into_response();
+            return IngestionError::InvalidProtobuf.into_response();
         }
     };
 
@@ -178,18 +224,18 @@ async fn handle_remote_write(
         }
         Err(Error::Storage(msg)) if msg.contains("buffer full") => {
             warn!("Write buffer full, returning 429");
-            service.metrics.requests_failed.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
+            service.metrics.requests_failed.fetch_add(1, Ordering::Relaxed);
             IngestionError::Backpressure.into_response()
         }
         Err(Error::InvalidLabel(msg)) => {
             warn!("Invalid labels: {}", msg);
-            service.metrics.requests_failed.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
-            IngestionError::InvalidLabels(msg).into_response()
+            service.metrics.requests_failed.fetch_add(1, Ordering::Relaxed);
+            IngestionError::InvalidLabels.into_response()
         }
         Err(e) => {
             error!("Failed to process write request: {}", e);
-            service.metrics.requests_failed.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
-            IngestionError::StorageError(e.to_string()).into_response()
+            service.metrics.requests_failed.fetch_add(1, Ordering::Relaxed);
+            IngestionError::StorageError.into_response()
         }
     }
 }
@@ -271,10 +317,10 @@ fn compute_series_fingerprint(labels: &[nightlight_types::Label]) -> u64 {
 #[derive(Debug)]
 enum IngestionError {
     PayloadTooLarge,
-    DecompressionFailed(String),
-    InvalidProtobuf(String),
-    InvalidLabels(String),
-    StorageError(String),
+    DecompressionFailed,
+    InvalidProtobuf,
+    InvalidLabels,
+    StorageError,
     Backpressure,
 }
 
@@ -284,16 +330,16 @@ impl IntoResponse for IngestionError {
             IngestionError::PayloadTooLarge => {
                 (StatusCode::PAYLOAD_TOO_LARGE, "Request payload too large")
             }
-            IngestionError::DecompressionFailed(_) => {
+            IngestionError::DecompressionFailed => {
                 (StatusCode::BAD_REQUEST, "Snappy decompression failed")
             }
-            IngestionError::InvalidProtobuf(_) => {
+            IngestionError::InvalidProtobuf => {
                 (StatusCode::BAD_REQUEST, "Invalid protobuf encoding")
             }
-            IngestionError::InvalidLabels(_) => {
+            IngestionError::InvalidLabels => {
                 (StatusCode::BAD_REQUEST, "Invalid metric labels")
             }
-            IngestionError::StorageError(_) => {
+            IngestionError::StorageError => {
                 (StatusCode::INTERNAL_SERVER_ERROR, "Storage error")
             }
             IngestionError::Backpressure => {
@@ -308,6 +354,7 @@ impl IntoResponse for IngestionError {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::storage::Storage;
 
     #[test]
     fn test_validate_labels_success() {
@@ -378,16 +425,58 @@ mod tests {
 
     #[tokio::test]
     async fn test_ingestion_service_storage() {
-        use crate::query::QueryableStorage;
-        use std::collections::HashMap;
-
-        let storage = Arc::new(RwLock::new(QueryableStorage {
-            series: HashMap::new(),
-            label_index: HashMap::new(),
-        }));
+        let dir = tempfile::tempdir().unwrap();
+        let storage = Arc::new(Storage::new(dir.path().to_str().unwrap()).unwrap());
         let service = IngestionService::new(storage);
-        let (samples, series) = service.storage_stats().await;
+        let (samples, series) = service.storage_stats().await.unwrap();
         assert_eq!(samples, 0);
         assert_eq!(series, 0);
     }
+
+    #[tokio::test]
+    async fn test_process_write_request_persists_samples() {
+        let dir = tempfile::tempdir().unwrap();
+        let storage = Arc::new(Storage::new(dir.path().to_str().unwrap()).unwrap());
+        let service = IngestionService::new(Arc::clone(&storage));
+
+        let request = WriteRequest {
+            timeseries: vec![nightlight_api::prometheus::TimeSeries {
+                labels: vec![
+                    Label {
+                        name: "__name__".to_string(),
+                        value: "ingest_metric".to_string(),
+                    },
+                    Label {
+                        name: "job".to_string(),
+                        value: "test".to_string(),
+                    },
+                ],
+                samples: vec![nightlight_api::prometheus::Sample {
+                    value: 42.0,
+                    timestamp: 1_000,
+                }],
+            }],
+        };
+
+        let processed = service.process_write_request(request).await.unwrap();
+        assert_eq!(processed, 1);
+
+        storage.flush().await.unwrap();
+        let reloaded = Storage::new(dir.path().to_str().unwrap()).unwrap();
+        let ids = reloaded
+            .find_series(vec![
+                "__name__=ingest_metric".to_string(),
+                "job=test".to_string(),
+            ])
+            .await
+            .unwrap();
+        assert_eq!(ids.len(), 1);
+        let series = reloaded
+            .query_series(ids[0], 0, 10_000)
+            .await
+            .unwrap()
+            .unwrap();
+        assert_eq!(series.samples.len(), 1);
+        assert_eq!(series.samples[0].value, 42.0);
+    }
 }
diff --git a/nightlight/crates/nightlight-server/src/lib.rs b/nightlight/crates/nightlight-server/src/lib.rs
index a547b0d..a72db3f 100644
--- a/nightlight/crates/nightlight-server/src/lib.rs
+++ b/nightlight/crates/nightlight-server/src/lib.rs
@@ -3,6 +3,7 @@
 //! This library exposes the internal modules for integration testing.
 
 pub mod config;
+pub mod grpc;
 pub mod ingestion;
 pub mod query;
 pub mod storage;
diff --git a/nightlight/crates/nightlight-server/src/main.rs b/nightlight/crates/nightlight-server/src/main.rs
index 7c9af1d..3250ed5 100644
--- a/nightlight/crates/nightlight-server/src/main.rs
+++ b/nightlight/crates/nightlight-server/src/main.rs
@@ -1,127 +1,202 @@
-//! Nightlight Server
+//! Nightlight server binary.
 //!
-//! A Prometheus-compatible metrics storage system with mTLS support.
-//!
-//! # Architecture
-//!
-//! - **Ingestion**: Prometheus remote_write API (HTTP POST with snappy compression)
-//! - **Query**: PromQL query engine (gRPC and HTTP APIs)
-//! - **Storage**: Time-series database with retention and compaction
-//! - **Security**: mTLS for all connections (following T027 patterns)
-//!
-//! # Configuration
-//!
-//! Configuration is loaded from a YAML file (default: config.yaml).
-//! See config.rs for the full configuration schema.
+//! Nightlight exposes:
+//! - Prometheus remote_write ingestion over HTTP
+//! - PromQL-compatible query endpoints over HTTP and gRPC
+//! - gRPC admin endpoints for health and stats
+//! - durable local storage backed by a WAL and snapshots
+
+use std::net::SocketAddr;
+use std::sync::Arc;
+use std::time::Duration;
 
 use anyhow::Result;
-use tracing::{info, Level};
+use axum::{routing::get, Router};
+use nightlight_api::nightlight::admin_server::AdminServer;
+use nightlight_api::nightlight::metric_query_server::MetricQueryServer;
+use tokio::time::MissedTickBehavior;
+use tonic::transport::Server as TonicServer;
+use tonic_health::server::health_reporter;
+use tracing::{error, info, warn, Level};
 
 mod config;
+mod grpc;
 mod ingestion;
 mod query;
 mod storage;
 
-use config::Config;
+use config::{Config, StorageConfig};
+use grpc::{AdminServiceImpl, MetricQueryServiceImpl};
+use ingestion::IngestionService;
+use query::QueryService;
+use storage::Storage;
+
+const DEFAULT_SNAPSHOT_INTERVAL_SECS: u64 = 30;
 
 #[tokio::main]
 async fn main() -> Result<()> {
-    // Initialize tracing subscriber for structured logging
     tracing_subscriber::fmt()
         .with_max_level(Level::INFO)
         .with_target(false)
         .with_thread_ids(true)
         .init();
 
-    info!("Nightlight server starting...");
+    info!("Nightlight server starting");
     info!("Version: {}", env!("CARGO_PKG_VERSION"));
 
-    // Load configuration from file or use defaults
     let mut config = match Config::from_file("config.yaml") {
-        Ok(cfg) => {
+        Ok(config) => {
             info!("Configuration loaded from config.yaml");
-            cfg
+            config
         }
-        Err(e) => {
-            info!("Failed to load config.yaml: {}, using defaults", e);
+        Err(error) => {
+            info!("Failed to load config.yaml: {}, using defaults", error);
             Config::default()
         }
     };
-
-    // Apply environment variable overrides (for NixOS module integration)
     config.apply_env_overrides();
 
+    if config.tls.is_some() {
+        warn!("Nightlight TLS configuration is currently ignored; starting plaintext listeners");
+    }
+
+    let http_addr: SocketAddr = config.server.http_addr.parse()?;
+    let grpc_addr: SocketAddr = config.server.grpc_addr.parse()?;
+    let storage = Arc::new(Storage::new(&config.storage.data_dir)?);
+    let query_service = QueryService::from_storage(storage.queryable());
+    let ingestion_service = IngestionService::new(Arc::clone(&storage));
+    let admin_service = AdminServiceImpl::new(
+        Arc::clone(&storage),
+        ingestion_service.metrics(),
+        query_service.metrics(),
+    );
+    let metric_query_service = MetricQueryServiceImpl::new(query_service.clone());
+
     info!("Server configuration:");
-    info!("  gRPC address: {}", config.server.grpc_addr);
-    info!("  HTTP address: {}", config.server.http_addr);
+    info!("  HTTP address: {}", http_addr);
+    info!("  gRPC address: {}", grpc_addr);
     info!("  Data directory: {}", config.storage.data_dir);
     info!("  Retention: {} days", config.storage.retention_days);
     info!(
-        "  TLS enabled: {}",
-        config.tls.as_ref().map_or("no", |_| "yes")
+        "  Compaction interval: {} seconds",
+        config.storage.compaction_interval_seconds
     );
 
-    // TODO (S5): Initialize storage layer
-    // let storage = storage::Storage::new(&config.storage)?;
-    // info!("Storage initialized");
+    let http_listener = tokio::net::TcpListener::bind(http_addr).await?;
+    let http_app = Router::new()
+        .route("/healthz", get(healthz))
+        .merge(ingestion_service.clone().router())
+        .merge(query_service.clone().router());
 
-    // S5: Load persistent state from disk
-    let data_path = std::path::PathBuf::from(&config.storage.data_dir)
-        .join("nightlight.db");
-    let query_service = query::QueryService::new_with_persistence(&data_path)?;
-    info!("Query service initialized");
+    let (mut health_reporter, health_service) = health_reporter();
+    health_reporter
+        .set_serving::<MetricQueryServer<MetricQueryServiceImpl>>()
+        .await;
+    health_reporter
+        .set_serving::<AdminServer<AdminServiceImpl>>()
+        .await;
 
-    // Initialize ingestion service with shared storage
-    let shared_storage = query_service.storage();
-    let ingestion_service = ingestion::IngestionService::new(shared_storage);
-    info!("Ingestion service initialized (sharing storage with query service)");
+    let (shutdown_tx, _) = tokio::sync::broadcast::channel::<()>(1);
+    let mut http_shutdown = shutdown_tx.subscribe();
+    let mut grpc_shutdown = shutdown_tx.subscribe();
+    let maintenance_shutdown = shutdown_tx.subscribe();
 
-    // Clone for shutdown handler
-    let query_service_for_shutdown = query_service.clone();
-    let data_path_for_shutdown = data_path.clone();
+    let http_server = async move {
+        axum::serve(http_listener, http_app)
+            .with_graceful_shutdown(async move {
+                let _ = http_shutdown.recv().await;
+            })
+            .await
+    };
 
-    // Create router with both ingestion and query endpoints
-    let app = ingestion_service.router().merge(query_service.router());
+    let grpc_server = TonicServer::builder()
+        .add_service(health_service)
+        .add_service(MetricQueryServer::new(metric_query_service))
+        .add_service(AdminServer::new(admin_service))
+        .serve_with_shutdown(grpc_addr, async move {
+            let _ = grpc_shutdown.recv().await;
+        });
 
-    // Start HTTP server for both ingestion and query endpoints
-    let listener = tokio::net::TcpListener::bind(&config.server.http_addr).await?;
-    info!("HTTP server listening on {}", config.server.http_addr);
+    let maintenance_handle = tokio::spawn(maintenance_loop(
+        Arc::clone(&storage),
+        config.storage.clone(),
+        maintenance_shutdown,
+    ));
+
+    info!("HTTP server listening on {}", http_addr);
     info!("  - Ingestion: POST /api/v1/write");
     info!("  - Query: GET /api/v1/query, /api/v1/query_range");
     info!("  - Metadata: GET /api/v1/series, /api/v1/label/:name/values");
+    info!("  - Health: GET /healthz");
+    info!("gRPC server listening on {}", grpc_addr);
+    info!("  - MetricQuery.InstantQuery / RangeQuery / SeriesQuery / LabelValuesQuery");
+    info!("  - Admin.Health / Stats / BuildInfo");
 
-    // TODO (S5): Start background tasks
-    // - Compaction
-    // - Retention enforcement
-    // - Metrics export
+    let shutdown = async {
+        tokio::signal::ctrl_c().await.expect("failed to install Ctrl+C handler");
+    };
+    tokio::pin!(shutdown);
 
-    info!("Nightlight server ready");
-    info!("Press Ctrl+C to shutdown");
+    tokio::select! {
+        result = http_server => {
+            result?;
+        }
+        result = grpc_server => {
+            result?;
+        }
+        _ = &mut shutdown => {
+            info!("Shutdown signal received");
+        }
+    }
 
-    // Serve with graceful shutdown
-    axum::serve(listener, app)
-        .with_graceful_shutdown(shutdown_signal(query_service_for_shutdown, data_path_for_shutdown))
-        .await?;
+    let _ = shutdown_tx.send(());
+    if let Err(error) = maintenance_handle.await {
+        error!(error = %error, "Nightlight maintenance task failed to join");
+    }
 
     info!("Nightlight server stopped");
     Ok(())
 }
 
-async fn shutdown_signal(
-    query_service: query::QueryService,
-    data_path: std::path::PathBuf,
+async fn maintenance_loop(
+    storage: Arc<Storage>,
+    config: StorageConfig,
+    mut shutdown: tokio::sync::broadcast::Receiver<()>,
 ) {
-    tokio::signal::ctrl_c()
-        .await
-        .expect("Failed to install CTRL+C handler");
-    info!("Shutdown signal received, saving data...");
+    let snapshot_interval_secs =
+        config.compaction_interval_seconds.clamp(5, DEFAULT_SNAPSHOT_INTERVAL_SECS);
+    let mut snapshot_interval = tokio::time::interval(Duration::from_secs(snapshot_interval_secs));
+    snapshot_interval.set_missed_tick_behavior(MissedTickBehavior::Delay);
 
-    // S5: Save persistent state to disk before shutdown
-    if let Err(e) = query_service.save_to_disk(&data_path).await {
-        tracing::error!("Failed to save data on shutdown: {}", e);
-    } else {
-        info!("Data saved successfully");
+    let mut retention_interval = tokio::time::interval(Duration::from_secs(
+        config.compaction_interval_seconds.max(1),
+    ));
+    retention_interval.set_missed_tick_behavior(MissedTickBehavior::Delay);
+
+    loop {
+        tokio::select! {
+            _ = shutdown.recv() => break,
+            _ = snapshot_interval.tick() => {
+                if let Err(error) = storage.flush().await {
+                    error!(error = %error, "Nightlight snapshot flush failed");
+                }
+            }
+            _ = retention_interval.tick() => {
+                if let Err(error) = storage.enforce_retention(config.retention_days).await {
+                    error!(error = %error, "Nightlight retention sweep failed");
+                }
+                if let Err(error) = storage.compact().await {
+                    error!(error = %error, "Nightlight compaction checkpoint failed");
+                }
+            }
+        }
     }
 
-    info!("Stopping server...");
+    if let Err(error) = storage.flush().await {
+        error!(error = %error, "Nightlight final snapshot flush failed");
+    }
+}
+
+async fn healthz() -> &'static str {
+    "ok"
 }
diff --git a/nightlight/crates/nightlight-server/src/query.rs b/nightlight/crates/nightlight-server/src/query.rs
index 7ef90c0..99c064b 100644
--- a/nightlight/crates/nightlight-server/src/query.rs
+++ b/nightlight/crates/nightlight-server/src/query.rs
@@ -6,10 +6,11 @@
 use axum::{
     extract::{Path, Query, State},
     http::StatusCode,
-    response::{IntoResponse, Json, Response},
+    response::{IntoResponse, Json},
     routing::get,
     Router,
 };
+use parking_lot::Mutex;
 use nightlight_types::{Error, Label, Result, Sample, SeriesId, TimeSeries};
 use promql_parser::{
     label::Matchers,
@@ -18,16 +19,21 @@ use promql_parser::{
     },
 };
 use serde::{Deserialize, Serialize};
-use std::collections::HashMap;
+use std::collections::{HashMap, VecDeque};
+use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
+use std::time::Instant;
 use tokio::sync::RwLock;
 use tracing::{debug, error, info};
 
+const QUERY_DURATION_HISTORY_LIMIT: usize = 512;
+
 /// Query service state
 #[derive(Clone)]
 pub struct QueryService {
     // Reference to queryable storage (shared with ingestion)
     storage: Arc<RwLock<QueryableStorage>>,
+    metrics: Arc<QueryMetrics>,
 }
 
 /// In-memory queryable storage (reads from ingestion buffer)
@@ -39,6 +45,24 @@ pub struct QueryableStorage {
     pub label_index: HashMap<String, HashMap<String, Vec<SeriesId>>>,
 }
 
+#[derive(Debug)]
+pub struct QueryMetrics {
+    queries_total: AtomicU64,
+    queries_failed: AtomicU64,
+    queries_active: AtomicU64,
+    durations_ms: Mutex<VecDeque<u64>>,
+}
+
+#[derive(Debug, Clone, Copy, Default)]
+pub struct QueryMetricsSnapshot {
+    pub queries_total: u64,
+    pub queries_failed: u64,
+    pub queries_active: u64,
+    pub query_duration_p50: f64,
+    pub query_duration_p95: f64,
+    pub query_duration_p99: f64,
+}
+
 impl QueryService {
     pub fn new() -> Self {
         Self {
@@ -46,12 +70,16 @@ impl QueryService {
                 series: HashMap::new(),
                 label_index: HashMap::new(),
             })),
+            metrics: Arc::new(QueryMetrics::new()),
         }
     }
 
     /// Create QueryService from existing shared storage
     pub fn from_storage(storage: Arc<RwLock<QueryableStorage>>) -> Self {
-        Self { storage }
+        Self {
+            storage,
+            metrics: Arc::new(QueryMetrics::new()),
+        }
     }
 
     /// Create QueryService and load persistent state from disk if it exists
@@ -61,6 +89,7 @@ impl QueryService {
 
         Ok(Self {
             storage: Arc::new(RwLock::new(storage)),
+            metrics: Arc::new(QueryMetrics::new()),
         })
     }
 
@@ -82,17 +111,32 @@ impl QueryService {
             .with_state(self)
     }
 
+    pub fn metrics(&self) -> Arc<QueryMetrics> {
+        Arc::clone(&self.metrics)
+    }
+
     /// Execute an instant query at a specific timestamp
     pub async fn execute_instant_query(&self, query: &str, time: i64) -> Result<QueryResult> {
         debug!("Executing instant query: {} at time {}", query, time);
+        let started = self.metrics.begin_query();
 
         // Parse PromQL expression
         let expr = promql_parser::parser::parse(query)
-            .map_err(|e| Error::Query(format!("Parse error: {:?}", e)))?;
+            .map_err(|e| Error::Query(format!("Parse error: {:?}", e)));
+        let expr = match expr {
+            Ok(expr) => expr,
+            Err(error) => {
+                self.metrics.finish_query(started, false);
+                return Err(error);
+            }
+        };
 
         // Execute the expression
         let storage = self.storage.read().await;
-        let result = self.evaluate_expr(&expr, time, time, 0, &storage).await?;
+        let result = self.evaluate_expr(&expr, time, time, 0, &storage).await;
+        let success = result.is_ok();
+        self.metrics.finish_query(started, success);
+        let result = result?;
 
         Ok(QueryResult {
             result_type: "vector".to_string(),
@@ -123,10 +167,31 @@ impl QueryService {
             "Executing range query: {} from {} to {} step {}",
             query, start, end, step
         );
+        let started = self.metrics.begin_query();
+
+        if step <= 0 {
+            self.metrics.finish_query(started, false);
+            return Err(Error::InvalidTimeRange(
+                "range query step must be greater than zero".to_string(),
+            ));
+        }
+        if end < start {
+            self.metrics.finish_query(started, false);
+            return Err(Error::InvalidTimeRange(
+                "range query end must be greater than or equal to start".to_string(),
+            ));
+        }
 
         // Parse PromQL expression
         let expr = promql_parser::parser::parse(query)
-            .map_err(|e| Error::Query(format!("Parse error: {:?}", e)))?;
+            .map_err(|e| Error::Query(format!("Parse error: {:?}", e)));
+        let expr = match expr {
+            Ok(expr) => expr,
+            Err(error) => {
+                self.metrics.finish_query(started, false);
+                return Err(error);
+            }
+        };
 
         let storage = self.storage.read().await;
         let mut results: HashMap<String, RangeResult> = HashMap::new();
@@ -136,7 +201,14 @@ impl QueryService {
         while current_time <= end {
             let step_result = self
                 .evaluate_expr(&expr, current_time, end, step, &storage)
-                .await?;
+                .await;
+            let step_result = match step_result {
+                Ok(step_result) => step_result,
+                Err(error) => {
+                    self.metrics.finish_query(started, false);
+                    return Err(error);
+                }
+            };
 
             for ts in step_result {
                 // Create a unique key for this series based on labels
@@ -169,10 +241,12 @@ impl QueryService {
             current_time += step;
         }
 
-        Ok(RangeQueryResult {
+        let result = RangeQueryResult {
             result_type: "matrix".to_string(),
             result: results.into_values().collect(),
-        })
+        };
+        self.metrics.finish_query(started, true);
+        Ok(result)
     }
 
     /// Evaluate a PromQL expression (recursive with boxing for async)
@@ -589,9 +663,108 @@ impl QueryService {
         true
     }
 
-    /// Get storage handle (for ingestion integration)
-    pub fn storage(&self) -> Arc<RwLock<QueryableStorage>> {
-        self.storage.clone()
+    pub async fn series_metadata(
+        &self,
+        matchers: &[String],
+        start: Option<i64>,
+        end: Option<i64>,
+    ) -> Result<Vec<HashMap<String, String>>> {
+        let started = self.metrics.begin_query();
+        let storage = self.storage.read().await;
+        let series = self.matching_series(&storage, matchers, start, end);
+        let result = Ok(series
+            .into_iter()
+            .map(|ts| {
+                ts.labels
+                    .iter()
+                    .map(|label| (label.name.clone(), label.value.clone()))
+                    .collect()
+            })
+            .collect());
+        self.metrics.finish_query(started, true);
+        result
+    }
+
+    pub async fn label_values_for_matchers(
+        &self,
+        label_name: &str,
+        matchers: &[String],
+        start: Option<i64>,
+        end: Option<i64>,
+    ) -> Result<Vec<String>> {
+        let started = self.metrics.begin_query();
+        let storage = self.storage.read().await;
+        let mut values: Vec<String> = self
+            .matching_series(&storage, matchers, start, end)
+            .into_iter()
+            .filter_map(|series| series.get_label(label_name).map(str::to_string))
+            .collect();
+        values.sort();
+        values.dedup();
+        self.metrics.finish_query(started, true);
+        Ok(values)
+    }
+
+    fn matching_series(
+        &self,
+        storage: &QueryableStorage,
+        matchers: &[String],
+        start: Option<i64>,
+        end: Option<i64>,
+    ) -> Vec<TimeSeries> {
+        let parsed_matchers = parse_label_matchers(matchers);
+        storage
+            .series
+            .values()
+            .filter(|series| series_matches(series, &parsed_matchers))
+            .filter(|series| series_in_time_range(series, start, end))
+            .cloned()
+            .collect()
+    }
+}
+
+impl QueryMetrics {
+    fn new() -> Self {
+        Self {
+            queries_total: AtomicU64::new(0),
+            queries_failed: AtomicU64::new(0),
+            queries_active: AtomicU64::new(0),
+            durations_ms: Mutex::new(VecDeque::with_capacity(QUERY_DURATION_HISTORY_LIMIT)),
+        }
+    }
+
+    fn begin_query(&self) -> Instant {
+        self.queries_total.fetch_add(1, Ordering::Relaxed);
+        self.queries_active.fetch_add(1, Ordering::Relaxed);
+        Instant::now()
+    }
+
+    fn finish_query(&self, started: Instant, success: bool) {
+        if !success {
+            self.queries_failed.fetch_add(1, Ordering::Relaxed);
+        }
+        self.queries_active.fetch_sub(1, Ordering::Relaxed);
+
+        let elapsed_ms = started.elapsed().as_millis() as u64;
+        let mut durations = self.durations_ms.lock();
+        if durations.len() >= QUERY_DURATION_HISTORY_LIMIT {
+            durations.pop_front();
+        }
+        durations.push_back(elapsed_ms);
+    }
+
+    pub fn snapshot(&self) -> QueryMetricsSnapshot {
+        let mut sorted_durations: Vec<u64> = self.durations_ms.lock().iter().copied().collect();
+        sorted_durations.sort_unstable();
+
+        QueryMetricsSnapshot {
+            queries_total: self.queries_total.load(Ordering::Relaxed),
+            queries_failed: self.queries_failed.load(Ordering::Relaxed),
+            queries_active: self.queries_active.load(Ordering::Relaxed),
+            query_duration_p50: percentile(&sorted_durations, 0.50),
+            query_duration_p95: percentile(&sorted_durations, 0.95),
+            query_duration_p99: percentile(&sorted_durations, 0.99),
+        }
     }
 }
 
@@ -600,12 +773,15 @@ impl QueryableStorage {
     pub fn upsert_series(&mut self, series: TimeSeries) {
         // Update label index
         for label in &series.labels {
-            self.label_index
+            let series_ids = self
+                .label_index
                 .entry(label.name.clone())
                 .or_default()
                 .entry(label.value.clone())
-                .or_default()
-                .push(series.id);
+                .or_default();
+            if !series_ids.contains(&series.id) {
+                series_ids.push(series.id);
+            }
         }
 
         // Upsert series
@@ -624,11 +800,91 @@ impl QueryableStorage {
 
     /// Get label values for a specific label name
     pub fn label_values(&self, label_name: &str) -> Vec<String> {
-        self.label_index
+        let mut values: Vec<String> = self
+            .label_index
             .get(label_name)
             .map(|values| values.keys().cloned().collect())
-            .unwrap_or_default()
+            .unwrap_or_default();
+        values.sort();
+        values
     }
+
+    pub fn rebuild_index(&mut self) {
+        self.label_index.clear();
+        let series: Vec<TimeSeries> = self.series.values().cloned().collect();
+        for series in series {
+            for label in &series.labels {
+                self.label_index
+                    .entry(label.name.clone())
+                    .or_default()
+                    .entry(label.value.clone())
+                    .or_default()
+                    .push(series.id);
+            }
+        }
+    }
+
+    pub fn prune_before(&mut self, cutoff: i64) -> usize {
+        let mut removed_samples = 0usize;
+        self.series.retain(|_, series| {
+            let before = series.samples.len();
+            series.samples.retain(|sample| sample.timestamp >= cutoff);
+            removed_samples += before.saturating_sub(series.samples.len());
+            !series.samples.is_empty()
+        });
+        self.rebuild_index();
+        removed_samples
+    }
+}
+
+fn percentile(values: &[u64], quantile: f64) -> f64 {
+    if values.is_empty() {
+        return 0.0;
+    }
+
+    let index = ((values.len() - 1) as f64 * quantile).round() as usize;
+    values[index.min(values.len() - 1)] as f64
+}
+
+fn parse_label_matchers(matchers: &[String]) -> Vec<(String, String)> {
+    matchers
+        .iter()
+        .filter_map(|matcher| matcher.split_once('='))
+        .map(|(key, value)| {
+            (
+                key.trim().to_string(),
+                value.trim().trim_matches('"').to_string(),
+            )
+        })
+        .collect()
+}
+
+fn series_matches(series: &TimeSeries, matchers: &[(String, String)]) -> bool {
+    matchers.iter().all(|(key, value)| {
+        series
+            .labels
+            .iter()
+            .any(|label| &label.name == key && &label.value == value)
+    })
+}
+
+fn series_in_time_range(series: &TimeSeries, start: Option<i64>, end: Option<i64>) -> bool {
+    let Some((series_start, series_end)) = series.time_range() else {
+        return true;
+    };
+
+    if let Some(start) = start {
+        if series_end < start {
+            return false;
+        }
+    }
+    if let Some(end) = end {
+        if series_start > end {
+            return false;
+        }
+    }
+
+    true
 }
 
 /// HTTP handler for instant queries
@@ -696,46 +952,57 @@ async fn handle_range_query(
 async fn handle_label_values(
     State(service): State<QueryService>,
     Path(label_name): Path<String>,
+    Query(params): Query<SeriesQueryParams>,
 ) -> impl IntoResponse {
-    let storage = service.storage.read().await;
-    let values = storage.label_values(&label_name);
-
-    (
-        StatusCode::OK,
-        Json(LabelValuesResponse {
-            status: "success".to_string(),
-            data: values,
-        }),
-    )
+    match service
+        .label_values_for_matchers(&label_name, &params.matchers, params.start, params.end)
+        .await
+    {
+        Ok(values) => (
+            StatusCode::OK,
+            Json(LabelValuesResponse {
+                status: "success".to_string(),
+                data: values,
+            }),
+        )
+            .into_response(),
+        Err(error) => (
+            StatusCode::BAD_REQUEST,
+            Json(serde_json::json!({
+                "status": "error",
+                "error": error.to_string(),
+            })),
+        )
+            .into_response(),
+    }
 }
 
 /// HTTP handler for series metadata
 async fn handle_series(
     State(service): State<QueryService>,
-    Query(_params): Query<SeriesQueryParams>,
+    Query(params): Query<SeriesQueryParams>,
 ) -> impl IntoResponse {
-    let storage = service.storage.read().await;
-
-    // Return all series metadata (limited implementation)
-    let series: Vec<HashMap<String, String>> = storage
-        .series
-        .values()
-        .take(1000) // Limit to prevent OOM
-        .map(|ts| {
-            ts.labels
-                .iter()
-                .map(|l| (l.name.clone(), l.value.clone()))
-                .collect()
-        })
-        .collect();
-
-    (
-        StatusCode::OK,
-        Json(SeriesResponse {
-            status: "success".to_string(),
-            data: series,
-        }),
-    )
+    match service
+        .series_metadata(&params.matchers, params.start, params.end)
+        .await
+    {
+        Ok(series) => (
+            StatusCode::OK,
+            Json(SeriesResponse {
+                status: "success".to_string(),
+                data: series,
+            }),
+        )
+            .into_response(),
+        Err(error) => (
+            StatusCode::BAD_REQUEST,
+            Json(serde_json::json!({
+                "status": "error",
+                "error": error.to_string(),
+            })),
+        )
+            .into_response(),
+    }
 }
 
 // Request/Response Types
@@ -760,6 +1027,10 @@ struct SeriesQueryParams {
     #[serde(default)]
     #[serde(rename = "match[]")]
     matchers: Vec<String>,
+    #[serde(default)]
+    start: Option<i64>,
+    #[serde(default)]
+    end: Option<i64>,
 }
 
 #[derive(Debug, Serialize)]
@@ -770,30 +1041,30 @@ struct QueryResponse {
     error_type: Option<String>,
 }
 
-#[derive(Debug, Serialize)]
-pub(crate) struct QueryResult {
+#[derive(Debug, Clone, Serialize)]
+pub struct QueryResult {
     #[serde(rename = "resultType")]
-    result_type: String,
-    result: Vec<InstantQueryResult>,
+    pub result_type: String,
+    pub result: Vec<InstantQueryResult>,
 }
 
-#[derive(Debug, Serialize)]
-struct InstantQueryResult {
-    metric: HashMap<String, String>,
-    value: Option<(i64, f64)>,
+#[derive(Debug, Clone, Serialize)]
+pub struct InstantQueryResult {
+    pub metric: HashMap<String, String>,
+    pub value: Option<(i64, f64)>,
 }
 
-#[derive(Debug, Serialize)]
-pub(crate) struct RangeQueryResult {
+#[derive(Debug, Clone, Serialize)]
+pub struct RangeQueryResult {
     #[serde(rename = "resultType")]
-    result_type: String,
-    result: Vec<RangeResult>,
+    pub result_type: String,
+    pub result: Vec<RangeResult>,
 }
 
-#[derive(Debug, Serialize)]
-struct RangeResult {
-    metric: HashMap<String, String>,
-    values: Vec<(i64, f64)>,
+#[derive(Debug, Clone, Serialize)]
+pub struct RangeResult {
+    pub metric: HashMap<String, String>,
+    pub values: Vec<(i64, f64)>,
 }
 
 #[derive(Debug, Serialize)]
@@ -808,29 +1079,6 @@ struct SeriesResponse {
     data: Vec<HashMap<String, String>>,
 }
 
-#[derive(Debug)]
-enum QueryError {
-    ParseFailed(String),
-    ExecutionFailed(String),
-}
-
-impl IntoResponse for QueryError {
-    fn into_response(self) -> Response {
-        let (status, message) = match self {
-            QueryError::ParseFailed(msg) => (StatusCode::BAD_REQUEST, msg),
-            QueryError::ExecutionFailed(msg) => (StatusCode::INTERNAL_SERVER_ERROR, msg),
-        };
-
-        let body = serde_json::json!({
-            "status": "error",
-            "errorType": "execution",
-            "error": message
-        });
-
-        (status, Json(body)).into_response()
-    }
-}
-
 impl Default for QueryService {
     fn default() -> Self {
         Self::new()
@@ -892,8 +1140,9 @@ impl QueryableStorage {
             .map_err(|e| Error::Storage(format!("Failed to read file: {}", e)))?;
 
         // Deserialize from bincode
-        let storage = bincode::deserialize(&buffer)
+        let mut storage: Self = bincode::deserialize(&buffer)
             .map_err(|e| Error::Storage(format!("Deserialization failed: {}", e)))?;
+        storage.rebuild_index();
 
         Ok(storage)
     }
diff --git a/nightlight/crates/nightlight-server/src/storage.rs b/nightlight/crates/nightlight-server/src/storage.rs
index 8da4126..620a315 100644
--- a/nightlight/crates/nightlight-server/src/storage.rs
+++ b/nightlight/crates/nightlight-server/src/storage.rs
@@ -1,12 +1,8 @@
-//! Time-series storage layer
-//!
-//! シンプルなWAL付きストレージ実装（S5足場）。
-//! - in-memory head: `QueryableStorage` を共有
-//! - WAL: bincode長さプレフィックスでappend / replay
-//! - スナップショット: `nightlight.db` にbincode保存
-//! - Retention/compactionは将来タスク（現状no-op）
+//! Time-series storage layer backed by an in-memory head, a write-ahead log,
+//! and periodic snapshots.
 
 use anyhow::Result;
+use chrono::Utc;
 use nightlight_types::{SeriesId, TimeSeries};
 use std::{
     fs::{File, OpenOptions},
@@ -15,16 +11,15 @@ use std::{
     sync::Arc,
 };
 use tokio::sync::{Mutex, RwLock};
+use tracing::debug;
 
 use crate::query::QueryableStorage;
 
-/// WALレコード
 #[derive(serde::Serialize, serde::Deserialize)]
 struct WalRecord {
     series: TimeSeries,
 }
 
-/// ストレージ本体
 pub struct Storage {
     head: Arc<RwLock<QueryableStorage>>,
     wal_path: PathBuf,
@@ -33,7 +28,6 @@ pub struct Storage {
 }
 
 impl Storage {
-    /// data_dirを初期化し、snapshot + WALをリプレイする
     pub fn new(data_dir: &str) -> Result<Self> {
         let data_dir = PathBuf::from(data_dir);
         std::fs::create_dir_all(&data_dir)?;
@@ -41,12 +35,11 @@ impl Storage {
         let snapshot_path = data_dir.join("nightlight.db");
         let wal_path = data_dir.join("wal.log");
 
-        // snapshotロード
         let mut head = QueryableStorage::load_from_file(&snapshot_path)?;
-        // WALリプレイ
         if wal_path.exists() {
             replay_wal(&wal_path, &mut head)?;
         }
+        head.rebuild_index();
 
         Ok(Self {
             head: Arc::new(RwLock::new(head)),
@@ -56,13 +49,15 @@ impl Storage {
         })
     }
 
-    /// 共有QueryableStorageを取得
     pub fn queryable(&self) -> Arc<RwLock<QueryableStorage>> {
-        self.head.clone()
+        Arc::clone(&self.head)
     }
 
-    /// WALへappendし、headへ反映
     pub async fn append(&self, series_list: Vec<TimeSeries>) -> Result<()> {
+        if series_list.is_empty() {
+            return Ok(());
+        }
+
         let _guard = self.wal_lock.lock().await;
         let mut wal_file = OpenOptions::new()
             .create(true)
@@ -78,14 +73,12 @@ impl Storage {
             let len = encoded.len() as u32;
             wal_file.write_all(&len.to_le_bytes())?;
             wal_file.write_all(&encoded)?;
-
             head.upsert_series(series);
         }
         wal_file.flush()?;
         Ok(())
     }
 
-    /// 指定IDのシリーズを時間範囲で返す
     pub async fn query_series(
         &self,
         series_id: SeriesId,
@@ -93,110 +86,142 @@ impl Storage {
         end: i64,
     ) -> Result<Option<TimeSeries>> {
         let head = self.head.read().await;
-        if let Some(series) = head.series.get(&series_id) {
-            let mut filtered = series.clone();
-            filtered
-                .samples
-                .retain(|s| s.timestamp >= start && s.timestamp <= end);
-            return Ok(Some(filtered));
-        }
-        Ok(None)
+        Ok(head
+            .series
+            .get(&series_id)
+            .map(|series| series.filter_by_time(start, end)))
     }
 
-    /// 簡易ラベル一致検索
     pub async fn find_series(&self, matchers: Vec<String>) -> Result<Vec<SeriesId>> {
         let parsed: Vec<(String, String)> = matchers
             .iter()
-            .filter_map(|m| m.split_once('='))
-            .map(|(k, v)| (k.to_string(), v.to_string()))
+            .filter_map(|matcher| matcher.split_once('='))
+            .map(|(key, value)| {
+                (
+                    key.trim().to_string(),
+                    value.trim().trim_matches('"').to_string(),
+                )
+            })
             .collect();
 
         let head = self.head.read().await;
         let mut result = Vec::new();
-        'outer: for (series_id, ts) in &head.series {
-            for (k, v) in &parsed {
-                if !ts.labels.iter().any(|l| &l.name == k && &l.value == v) {
+        'outer: for (series_id, series) in &head.series {
+            for (key, value) in &parsed {
+                if !series
+                    .labels
+                    .iter()
+                    .any(|label| &label.name == key && &label.value == value)
+                {
                     continue 'outer;
                 }
             }
             result.push(*series_id);
         }
+        result.sort_unstable();
         Ok(result)
     }
 
-    /// スナップショット保存 + WAL truncate
     pub async fn flush(&self) -> Result<()> {
-        let head = self.head.read().await;
-        head.save_to_file(&self.snapshot_path)?;
-        drop(head);
-
         let _guard = self.wal_lock.lock().await;
-        File::create(&self.wal_path)?; // truncate
+        let snapshot = {
+            let head = self.head.read().await;
+            head.clone()
+        };
+        snapshot.save_to_file(&self.snapshot_path)?;
+        File::create(&self.wal_path)?;
         Ok(())
     }
 
-    /// Retentionは将来実装（no-op）
-    pub async fn enforce_retention(&self, _retention_days: u32) -> Result<()> {
+    pub async fn enforce_retention(&self, retention_days: u32) -> Result<()> {
+        if retention_days == 0 {
+            return Ok(());
+        }
+
+        let retention_ms = i64::from(retention_days) * 24 * 60 * 60 * 1000;
+        let cutoff = Utc::now().timestamp_millis() - retention_ms;
+        let removed_samples = {
+            let mut head = self.head.write().await;
+            head.prune_before(cutoff)
+        };
+
+        if removed_samples > 0 {
+            debug!(removed_samples, cutoff, "pruned expired Nightlight samples");
+        }
+
         Ok(())
     }
 
-    /// Compactionは将来実装（no-op）
     pub async fn compact(&self) -> Result<()> {
-        Ok(())
+        self.flush().await
     }
 
-    /// 現在の統計
     pub async fn stats(&self) -> Result<StorageStats> {
         let head = self.head.read().await;
-        let active_series = head.series.len() as u64;
-        let total_samples = head
+        let total_samples: u64 = head
             .series
             .values()
-            .map(|s| s.samples.len() as u64)
+            .map(|series| series.samples.len() as u64)
             .sum();
-
+        let oldest_sample_time = head
+            .series
+            .values()
+            .filter_map(|series| series.oldest_sample().map(|sample| sample.timestamp))
+            .min()
+            .unwrap_or(0);
+        let newest_sample_time = head
+            .series
+            .values()
+            .filter_map(|series| series.latest_sample().map(|sample| sample.timestamp))
+            .max()
+            .unwrap_or(0);
         let wal_size = std::fs::metadata(&self.wal_path)
-            .map(|m| m.len())
+            .map(|metadata| metadata.len())
             .unwrap_or(0);
         let snapshot_size = std::fs::metadata(&self.snapshot_path)
-            .map(|m| m.len())
+            .map(|metadata| metadata.len())
             .unwrap_or(0);
 
         Ok(StorageStats {
-            active_series,
+            active_series: head.series.len() as u64,
             total_samples,
-            blocks_count: 1,
+            blocks_count: u64::from(snapshot_size > 0),
+            head_samples: total_samples,
             disk_bytes_used: wal_size + snapshot_size,
+            oldest_sample_time,
+            newest_sample_time,
         })
     }
 }
 
-/// WALリプレイ
 fn replay_wal(path: &Path, storage: &mut QueryableStorage) -> Result<()> {
     let mut file = File::open(path)?;
     let mut len_buf = [0u8; 4];
     loop {
-        if let Err(e) = file.read_exact(&mut len_buf) {
-            if e.kind() == std::io::ErrorKind::UnexpectedEof {
+        if let Err(error) = file.read_exact(&mut len_buf) {
+            if error.kind() == std::io::ErrorKind::UnexpectedEof {
                 break;
             }
-            return Err(e.into());
+            return Err(error.into());
         }
         let len = u32::from_le_bytes(len_buf) as usize;
-        let mut buf = vec![0u8; len];
-        file.read_exact(&mut buf)?;
-        let record: WalRecord = bincode::deserialize(&buf)?;
+        let mut buffer = vec![0u8; len];
+        file.read_exact(&mut buffer)?;
+        let record: WalRecord = bincode::deserialize(&buffer)?;
         storage.upsert_series(record.series);
     }
     Ok(())
 }
 
-/// Storage statistics
+#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
 pub struct StorageStats {
     pub active_series: u64,
     pub total_samples: u64,
     pub blocks_count: u64,
+    pub head_samples: u64,
     pub disk_bytes_used: u64,
+    pub oldest_sample_time: i64,
+    pub newest_sample_time: i64,
 }
 
 #[cfg(test)]
@@ -247,6 +272,76 @@ mod tests {
         assert_eq!(res.samples[1].value, 2.0);
     }
 
+    #[tokio::test]
+    async fn test_retention_prunes_old_samples_and_series() {
+        let dir = tempfile::tempdir().unwrap();
+        let storage = Storage::new(dir.path().to_str().unwrap()).unwrap();
+        let now = Utc::now().timestamp_millis();
+
+        storage
+            .append(vec![
+                TimeSeries {
+                    id: SeriesId::new(1),
+                    labels: vec![Label::new("__name__", "retained_metric")],
+                    samples: vec![
+                        nightlight_types::Sample::new(now - (2 * 24 * 60 * 60 * 1000), 1.0),
+                        nightlight_types::Sample::new(now, 2.0),
+                    ],
+                },
+                TimeSeries {
+                    id: SeriesId::new(2),
+                    labels: vec![Label::new("__name__", "expired_metric")],
+                    samples: vec![nightlight_types::Sample::new(
+                        now - (3 * 24 * 60 * 60 * 1000),
+                        3.0,
+                    )],
+                },
+            ])
+            .await
+            .unwrap();
+
+        storage.enforce_retention(1).await.unwrap();
+
+        let retained = storage
+            .query_series(SeriesId::new(1), 0, now + 1)
+            .await
+            .unwrap()
+            .unwrap();
+        assert_eq!(retained.samples.len(), 1);
+        assert_eq!(retained.samples[0].value, 2.0);
+
+        let expired = storage
+            .query_series(SeriesId::new(2), 0, now + 1)
+            .await
+            .unwrap();
+        assert!(expired.is_none());
+    }
+
+    #[tokio::test]
+    async fn test_stats_report_sample_bounds() {
+        let dir = tempfile::tempdir().unwrap();
+        let storage = Storage::new(dir.path().to_str().unwrap()).unwrap();
+
+        storage
+            .append(vec![TimeSeries {
+                id: SeriesId::new(99),
+                labels: vec![Label::new("__name__", "stats_metric")],
+                samples: vec![
+                    nightlight_types::Sample::new(1000, 1.0),
+                    nightlight_types::Sample::new(2000, 2.0),
+                ],
+            }])
+            .await
+            .unwrap();
+
+        let stats = storage.stats().await.unwrap();
+        assert_eq!(stats.active_series, 1);
+        assert_eq!(stats.total_samples, 2);
+        assert_eq!(stats.head_samples, 2);
+        assert_eq!(stats.oldest_sample_time, 1000);
+        assert_eq!(stats.newest_sample_time, 2000);
+    }
+
     #[tokio::test]
     async fn test_find_series() {
         let dir = tempfile::tempdir().unwrap();
diff --git a/nix/test-cluster/run-cluster.sh b/nix/test-cluster/run-cluster.sh
index 91a6db9..f4d84a6 100755
--- a/nix/test-cluster/run-cluster.sh
+++ b/nix/test-cluster/run-cluster.sh
@@ -75,6 +75,9 @@ CREDITSERVICE_PROTO_DIR="${REPO_ROOT}/creditservice/proto"
 CREDITSERVICE_PROTO="${CREDITSERVICE_PROTO_DIR}/creditservice.proto"
 LIGHTNINGSTOR_PROTO_DIR="${REPO_ROOT}/lightningstor/crates/lightningstor-api/proto"
 LIGHTNINGSTOR_PROTO="${LIGHTNINGSTOR_PROTO_DIR}/lightningstor.proto"
+NIGHTLIGHT_PROTO_DIR="${REPO_ROOT}/nightlight/crates/nightlight-api/proto"
+NIGHTLIGHT_QUERY_PROTO="${NIGHTLIGHT_PROTO_DIR}/query.proto"
+NIGHTLIGHT_ADMIN_PROTO="${NIGHTLIGHT_PROTO_DIR}/admin.proto"
 PLASMAVMC_PROTO_DIR="${REPO_ROOT}/plasmavmc/proto"
 PLASMAVMC_PROTO="${PLASMAVMC_PROTO_DIR}/plasmavmc.proto"
 FLAREDB_PROTO_DIR="${REPO_ROOT}/flaredb/crates/flaredb-proto/src"
@@ -4676,10 +4679,24 @@ validate_nightlight_flow_with_base() {
     --label source=smoke \
     --label cluster=photoncloud
 
+  wait_for_nightlight_query_result "${base_url}" "${flow_name}" "${metric_name}" "${metric_value}" "source=\"smoke\""
+
+  curl -fsS "${base_url}/label/__name__/values" \
+    | jq -e --arg name "${metric_name}" '.status == "success" and (.data | index($name)) != null' >/dev/null
+  curl -fsS "${base_url}/series" \
+    | jq -e --arg name "${metric_name}" '.status == "success" and (.data | any(.__name__ == $name))' >/dev/null
+}
+
+wait_for_nightlight_query_result() {
+  local base_url="$1"
+  local flow_name="$2"
+  local metric_name="$3"
+  local metric_value="$4"
+  local selector_suffix="${5:-}"
   local deadline=$((SECONDS + HTTP_WAIT_TIMEOUT))
   while true; do
     if curl -fsS --get "${base_url}/query" \
-      --data-urlencode "query=${metric_name}{source=\"smoke\"}" \
+      --data-urlencode "query=${metric_name}{${selector_suffix}}" \
       | jq -e --arg name "${metric_name}" --argjson expected "${metric_value}" '
         .status == "success"
         and (.data.result | length) >= 1
@@ -4692,15 +4709,11 @@ validate_nightlight_flow_with_base() {
     fi
     sleep 2
   done
-
-  curl -fsS "${base_url}/label/__name__/values" \
-    | jq -e --arg name "${metric_name}" '.status == "success" and (.data | index($name)) != null' >/dev/null
-  curl -fsS "${base_url}/series" \
-    | jq -e --arg name "${metric_name}" '.status == "success" and (.data | any(.__name__ == $name))' >/dev/null
 }
 
 validate_nightlight_flow() {
   validate_nightlight_flow_with_base "http://127.0.0.1:9090/api/v1" "NightLight"
+  validate_nightlight_grpc_and_persistence
 }
 
 validate_apigateway_nightlight_flow() {
@@ -4709,6 +4722,85 @@ validate_apigateway_nightlight_flow() {
   validate_nightlight_flow_with_base "http://127.0.0.1:8080/api/v1/metrics" "API Gateway -> NightLight"
 }
 
+validate_nightlight_grpc_and_persistence() {
+  log "Validating NightLight gRPC query/admin APIs and restart persistence"
+
+  local base_url="http://127.0.0.1:9090/api/v1"
+  local grpc_tunnel=""
+  local metric_name="nightlight_persist_metric_$(date +%s)"
+  local metric_value
+  metric_value="$(awk 'BEGIN{srand(); printf "%.3f\n", (rand()*100)+1}')"
+
+  grpc_tunnel="$(start_ssh_tunnel node06 15090 50088)"
+  trap 'stop_ssh_tunnel node06 "${grpc_tunnel}"' RETURN
+
+  python3 "${REPO_ROOT}/nix/test-cluster/nightlight_remote_write.py" \
+    --url "${base_url}/write" \
+    --metric "${metric_name}" \
+    --value "${metric_value}" \
+    --label source=grpc \
+    --label cluster=photoncloud
+
+  wait_for_nightlight_query_result "${base_url}" "NightLight persistence pre-restart" "${metric_name}" "${metric_value}" "source=\"grpc\""
+
+  grpcurl -plaintext \
+    -import-path "${NIGHTLIGHT_PROTO_DIR}" \
+    -proto "${NIGHTLIGHT_QUERY_PROTO}" \
+    -d "$(jq -cn --arg query "${metric_name}{source=\"grpc\"}" '{query:$query, time:0, timeout:5000}')" \
+    127.0.0.1:15090 nightlight.MetricQuery/InstantQuery \
+    | jq -e --arg name "${metric_name}" --argjson expected "${metric_value}" '
+      .status == "success"
+      and (.data.result | any(.metric.__name__ == $name and (.value.value >= ($expected - 0.001)) and (.value.value <= ($expected + 0.001))))
+    ' >/dev/null
+
+  grpcurl -plaintext \
+    -import-path "${NIGHTLIGHT_PROTO_DIR}" \
+    -proto "${NIGHTLIGHT_QUERY_PROTO}" \
+    -d "$(jq -cn --arg match "__name__=${metric_name}" '{match:[$match]}')" \
+    127.0.0.1:15090 nightlight.MetricQuery/SeriesQuery \
+    | jq -e --arg name "${metric_name}" '.status == "success" and (.data | any(.labels.__name__ == $name))' >/dev/null
+
+  grpcurl -plaintext \
+    -import-path "${NIGHTLIGHT_PROTO_DIR}" \
+    -proto "${NIGHTLIGHT_QUERY_PROTO}" \
+    -d "$(jq -cn --arg label "source" --arg match "__name__=${metric_name}" '{labelName:$label, match:[$match]}')" \
+    127.0.0.1:15090 nightlight.MetricQuery/LabelValuesQuery \
+    | jq -e '.status == "success" and (.data | index("grpc")) != null' >/dev/null
+
+  grpcurl -plaintext \
+    -import-path "${NIGHTLIGHT_PROTO_DIR}" \
+    -proto "${NIGHTLIGHT_ADMIN_PROTO}" \
+    -d '{}' \
+    127.0.0.1:15090 nightlight.Admin/Health \
+    | jq -e '.status == "ok" and (.components | any(.name == "storage" and .status == "ok"))' >/dev/null
+
+  grpcurl -plaintext \
+    -import-path "${NIGHTLIGHT_PROTO_DIR}" \
+    -proto "${NIGHTLIGHT_ADMIN_PROTO}" \
+    -d '{}' \
+    127.0.0.1:15090 nightlight.Admin/Stats \
+    | jq -e '.storage.totalSamples >= 1 and .ingestion.samplesIngestedTotal >= 1 and .query.queriesTotal >= 1' >/dev/null
+
+  ssh_node node06 "systemctl restart nightlight.service"
+  wait_for_host_http http://127.0.0.1:9090/healthz
+  wait_for_tcp_port node06 50088
+
+  wait_for_nightlight_query_result "${base_url}" "NightLight persistence post-restart" "${metric_name}" "${metric_value}" "source=\"grpc\""
+
+  grpcurl -plaintext \
+    -import-path "${NIGHTLIGHT_PROTO_DIR}" \
+    -proto "${NIGHTLIGHT_QUERY_PROTO}" \
+    -d "$(jq -cn --arg query "${metric_name}{source=\"grpc\"}" '{query:$query, time:0, timeout:5000}')" \
+    127.0.0.1:15090 nightlight.MetricQuery/InstantQuery \
+    | jq -e --arg name "${metric_name}" --argjson expected "${metric_value}" '
+      .status == "success"
+      and (.data.result | any(.metric.__name__ == $name and (.value.value >= ($expected - 0.001)) and (.value.value <= ($expected + 0.001))))
+    ' >/dev/null
+
+  trap - RETURN
+  stop_ssh_tunnel node06 "${grpc_tunnel}"
+}
+
 validate_creditservice_rest_flow() {
   local base_url="$1"
   local token="$2"