A developer created reusable code that several AWS Lambda functions need to use.

A Lambda layer is the correct operationally efficient solution because layers are specifically designed to package reusable code, libraries, custom runtimes, or configuration files separately from function code. The developer can publish the shared .zip archive as a layer version and attach that layer to multiple Lambda functions. This avoids copying the same dependency into every deployment package and centralizes dependency management. Amazon S3 alone does not create an importable runtime dependency path for Lambda. A separate Lambda function would add synchronous invocation latency and coupling. A container image could work for container-based functions, but it is heavier and unnecessary when the code is already packaged as a .zip dependency. AWS documentation states that layers are used to separate reusable dependencies from function code and add them to functions. ( AWS Documentation )

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