Architecture

How to implement the transactional outbox pattern for reliable event publishing, including schema design, relay claiming, retries, duplicate handling, ordering, CDC, monitoring, and cleanup.

A practical rollout plan for safe database migrations using expand-and-contract, phased constraints, resumable backfills, rollback planning, and production monitoring.

How to version APIs without breaking existing clients, including compatibility policy, breaking-change examples, staged v1 to v2 rollout, deprecation headers, telemetry, and release gates.

Why adding more service instances can leave throughput flat when the bottleneck is a shared database, lock, connection pool, external dependency, queue, cache, or load-balancing constraint.

Why read replicas often fail to reduce primary database load when reads are coupled to writes, replica lag triggers fallback behavior, and query cost is misunderstood.