ADR-0013: Raft-replicated KV storage

Status

Accepted (Phase 9)

Context

Functions and the control plane need strongly consistent shared state. openraft was evaluated; a compact in-tree Raft core was preferred for Windows CI simplicity and zero extra native deps.

Decision

• Ship a compact Raft implementation (src/raft_kv.rs): leader election, log replication, commit/apply, single- and multi-node tests.
• KvStore wraps a shared RaftNode; single-node lab mode commits immediately; multi-node uses replicate_to.
• Expose KV via REST (/v1/kv) and optional Wasm host imports (chimera.kv_get_i32 / chimera.kv_set_i32).
• SQL / relational layer: not shipped. Prefer correct Raft KV + secondary indexes later. SQL is roadmap.

Honesty

Network transport over QUIC for Raft RPCs is pluggable/hooks-ready; unit tests use in-process replication. Production mesh wiring of Raft over QUIC remains incremental.

Consequences

Correctness tests gate merges. Do not advertise SQL until a feature-gated engine exists.