Lambda
AWS Lambda is Amazon's serverless function-as-a-service (FaaS). It runs short-lived functions in response to events, scales transparently from zero to thousands of concurrent invocations, and bills only for execution time. Lambda is the foundational serverless service in AWS and the pattern most other clouds modelled their FaaS offerings on.
How it works
Code is packaged as a deployment artifact (zip file or container image) and uploaded to Lambda. An event source (API Gateway, S3, SQS, EventBridge, DynamoDB Streams, ALB, scheduled rule) invokes the function with an event payload. Lambda provisions an execution environment, runs the handler, and tears it down (or keeps it warm for subsequent invocations).
Key limits and characteristics
- Memory. 128 MB to 10,240 MB; CPU scales with memory.
- Timeout. Up to 15 minutes per invocation.
- Concurrency. Each region has a quota; reserved and provisioned concurrency control allocation.
- Cold start. First invocation after a function scales down pays initialization overhead; mitigated by SnapStart (Java), provisioned concurrency, or lighter runtimes.
- Languages. Native runtimes for Node.js, Python, Java, Go, .NET, Ruby; custom runtimes via the Runtime API or container images.
Common use cases
- HTTP APIs behind API Gateway or ALB
- Stream and queue processing
- S3 event reactions (image resizing, metadata extraction)
- Scheduled jobs and cron replacement
- Edge logic via Lambda@Edge or CloudFront Functions
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