Guide on AWS Lambda Layers

AWS Lambda Layers is an important concept to grasp for any AWS Solution Architect.

What are Lambda Layers?
They are a distribution mechanism for libraries, custom runtimes, and other function dependencies. Layers promote code sharing and separation of responsibilities so that you can iterate faster on writing business logic.

Why are Lambda Layers important?
Lambda Layers allow you to manage your in-development AWS Lambda function’s code and resources more effectively, which can even lead to substantial cost reduction. They serve to separate your function’s code from its resources, sparing you much of the effort and resources previously taken up by bundling them together.

How do Lambda Layers work?
In a Lambda deployment package, dependencies are included alongside your code. When using layers, these dependencies are moved out of the deployment package and into a layer which is a .zip file that contains libraries, a custom runtime, or other dependencies. The layer is uploaded to Lambda, and the ARNs of those layers are then specified when you create a function.

Exam Tips: Answering Questions on Lambda Layers
- Remember that layers decouple your function code from its dependencies.
- Lambda function and its associated layers must be in the same region.
- A Lambda Layer can be used in any number of AWS Lambda functions.
- The total unzipped size of the function and all layers cannot exceed the unzipped deployment package size limit of 250 MB.

Lambda Layers is a powerful tool in a solution architect’s arsenal, making function updates easier, promoting code sharing and separation of responsibilities, and can potentially result in reduced costs.