Collab Phase 6: Idempotent Overwrite and Conflict Payload Enhancements for Deferred Commit Clients

[cubap]

Summary

Enhance RERUM durability APIs for deferred commit workloads with idempotency and richer conflict metadata.

Scope

• Support idempotency keys for overwrite and retry safety.
• Ensure conflict responses include current revision and current document metadata.
• Evaluate optional bulk overwrite endpoint for batched page flushes.
• Emit metrics for write rate, conflict rate, and latency.

Acceptance Criteria

• Retries using same idempotency key do not duplicate writes.
• Conflict response contains fields needed for client reconciliation.
• Metrics are emitted for durability observability.

Dependency

• Aligns with TPEN services durable flush worker issue.