What is AWS Lambda, and what are its key limits (timeout, memory, package size)?
AWS · Intermediate level
Answer
Lambda runs code in response to events without managing servers. Key limits include a 15-minute maximum timeout, memory configuration, concurrency controls, package/container size considerations, payload limits, and temporary storage configuration.
Technical explanation
Concurrency limits and downstream capacity are often more important operationally than the function code itself.
Serverless design shifts server operations to AWS but increases the importance of event semantics, timeouts, retries, idempotency, concurrency, and downstream protection.
Observability must include structured logs, metrics, traces, DLQs or failure destinations, and alarms on errors, throttles, duration, and age/lag where applicable.
Cold starts, package size, runtime choice, and VPC dependencies should be measured against p95/p99 latency rather than assumed.
Hands-on example
1. Build a small event-driven flow using Lambda plus the relevant event source such as API Gateway, S3, SQS, or EventBridge.
2. Configure timeout, memory, reserved concurrency, IAM role, structured logs, metrics, tracing, and DLQ or failure destination.
3. Inject duplicate events, timeouts, and downstream failures to validate retries and idempotency.
4. Create alarms for errors, throttles, duration, iterator age or queue age, and DLQ messages.
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