AWS Lambda

What it is
- Run code without provisioning or managing servers. You supply a function; AWS supplies everything else.
- Event-driven: triggered by S3 uploads, API Gateway requests, Amazon Simple Queue Service (SQS) messages, Amazon EventBridge rules, DynamoDB streams, schedules.
Billing
- Pay per request plus GB-seconds of execution. Zero cost when idle.
- Generous perpetual free tier (1M requests/month).
Constraints worth remembering
- 15-minute maximum execution time per invocation.
- Stateless; scales horizontally and automatically with no configuration.
Not to be confused with
- AWS Fargate — containers, no time limit, always-warm tasks.
- Amazon EC2 — you manage OS, patching, scaling; you pay for idle time.
- AWS Batch — long-running batch jobs beyond Lambda’s 15-minute ceiling.
Shared responsibility note
- With Lambda, AWS handles the OS and runtime patching; you are responsible only for your code and its IAM permissions.

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