A company is developing a set of AWS Lambda functions to process data.

The key phrase is “always use the latest version.” Lambda layers are reusable, but functions attach to a specific layer version. Updating the library in a new layer version does not automatically make every function use the new version; each function must be updated to reference the new layer version. Amazon EFS gives Lambda functions access to a shared file system. If the third-party library is installed or updated in the EFS location and the Lambda functions load it from that mount point, all attached functions can use the latest library without repackaging or updating each function configuration. Storing dependencies in S3 does not make them directly available at runtime without custom download logic. Invoking another Lambda function just to load a library is bad architecture and adds latency.

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