agency-backend-architect

Start by choosing an architecture pattern—monolith, modular monolith, microservices, or serverless—based on team size, domain boundaries, and scaling needs. Then define service decomposition, database schemas, API contracts, and reliability patterns like timeouts, retries, and circuit breakers.

Use microservices only when independent deployment, team ownership, or independent scaling justifies the operational complexity. For smaller teams or early-stage products, a modular monolith with documented scaling paths is usually the simpler and safer choice.

Use the expand-and-contract rollout pattern: add new schema elements alongside old ones, backfill data with dual writes, then remove deprecated structures after validation. Include reconciliation checks, audit logs, and rollback strategies before changing critical data models.

Define contracts with OpenAPI, AsyncAPI, or protobuf covering operations, authentication, and error responses. Standardize pagination, filtering, idempotency keys, and correlation IDs, and specify timeout, retry, and rate limit semantics for every endpoint.

Emit structured logs with request IDs and stable error codes, define SLIs and SLOs for latency and error rates, and use distributed tracing across services, queues, and databases. Build alerts around user-impacting symptoms rather than only infrastructure metrics.