Design serverless apps for reliability, cold start, and cost. Event-driven patterns and observability.

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AWS Lambda and Serverless Best Practices for Production

Serverless fits event-driven and variable load. Use these practices to keep it reliable and cost-effective.

Cold Start and Performance #

Provisioned concurrency for latency-sensitive paths (or warm-up jobs).
Right-size memory (more memory = more CPU); benchmark to find the sweet spot.
Minimize package size: Tree-shake, avoid large deps; use layers for shared code.

Idempotency: Use a idempotency key (e.g. in DDB) for critical actions.
Dead-letter queues: Send failed events to DLQ; alert and replay.
Retries: Use Lambda retries with backoff; set max retries and reserved concurrency to avoid thundering herd.

Structured logs and trace IDs; send to CloudWatch Logs Insights or a third-party.
Metrics: Invocations, errors, duration, throttles; alarm on error rate and latency.

Best practice: treat Lambda as a building block; design event contracts and failure modes up front.