A Lambda Layer is a package of libraries or dependencies you can share across multiple functions, so you don’t bundle the same code into every function’s deployment package.
Why they exist
Layers keep your function packages small and your shared dependencies in one place — update the layer once and many functions benefit. The tell is “share common libraries across several Lambda functions” or “reduce duplication in deployment packages.”
Test yourself
Several Lambda functions all use the same set of heavy shared libraries, bloating each deployment package. What’s the cleanest fix?
- Copy the libraries into every function
- Publish the libraries as a Lambda Layer
- Store the libraries in S3 and download at runtime
- Increase each function’s package limit
👉 Click to reveal the answer & explanation
Correct answer: B. A Lambda Layer packages shared libraries once and is attached to many functions, keeping packages small and centralizing updates. Copying into each (A) duplicates; downloading from S3 at runtime (C) adds latency; raising limits (D) doesn’t reduce duplication.
Related topics
AWS Lambda · Lambda concurrency · Amazon S3
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