photoncloud-monorepo/specifications/flaredb/003-kvs-consistency/contracts/kv_cas.md

KvCas contracts (strong consistency)

CompareAndSwap

• RPC: kvrpc.KvCas/CompareAndSwap
• Request:
  • namespace: string (empty => default)
  • key: bytes
  • value: bytes
  • expected_version: uint64
• Response:
  • success: bool
  • current_version: uint64
  • new_version: uint64
• Semantics:
  • Allowed only for strong namespaces; returns FailedPrecondition otherwise or when not leader (redirect required).
  • Proposes via Raft; state machine applies with LWW timestamp wrapper.

Get

• RPC: kvrpc.KvCas/Get
• Request:
  • namespace: string (empty => default)
  • key: bytes
• Response:
  • found: bool
  • value: bytes
  • version: uint64
• Semantics:
  • Allowed only for strong namespaces; returns FailedPrecondition if not leader.
  • Reads versioned value (timestamp-prefixed) and returns decoded value plus version.