Avoid cold-start and timeout pitfalls calling AWS Lambda from an API
domain: aws-lambda · 4 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Invoke synchronously via API Gateway/Function URL, or async with InvocationType=Event
Set function timeout below the caller's timeout (API GW caps at 29s by default)
Initialize SDK clients outside the handler for connection reuse
For latency-critical paths configure provisioned concurrency
Known gotchas
API Gateway hard 29s integration timeout (raisable via quota request) — long work must go async + polling/webhook
Async invokes retry twice on error; make handlers idempotent or set maximum retry attempts to 0
Lambda in a VPC needs NAT for internet egress — calls to public APIs hang without it
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