Patterns and best practices for AWS serverless workloads. Use when the user asks about Lambda (cold starts, memory, concurrency, timeouts), Lambda Powertools (Logger, Tracer, Metrics), observability, CloudWatch alarms, event-driven architecture (SQS, SNS, EventBridge, Step Functions), or API Gateway (HTTP vs REST API, rate limiting, WAF, X-Ray tracing, going-live checklist). Triggers on: Lambda, cold start, Powertools, SQS, SNS, EventBridge, Step Functions, ECS vs Lambda, DLQ, event-driven, serverless, concurrency, provisioned concurrency, API Gateway, HTTP API, REST API, WAF, rate limiting.