I’m working with AWS Lambda and need to attach multiple Lambda layers to a function. I know that AWS allows you to specify the order of layers, but I’m unclear on how the ordering actually affects execution.
My questions are: 1. How does AWS determine which layer takes precedence when multiple layers contain files in the same directory (e.g., /python, /opt)? 2. If two layers contain the same module name or file path, which one “wins”? 3. Is there a best practice for ordering layers when combining: • a dependencies layer (e.g., Python libraries) • a shared utilities layer • third-party vendor layers 4. Does the order affect only file overriding, or also import resolution, environment variables, or something else? 5. What’s the safest way to structure layers so that conflicts are avoided?
I am using Python 3.x, and some of my layers share overlapping library names. I want to avoid unexpected shadowing or import issues.
Environment: • AWS Lambda (Python 3.8) (I know it's depracated) • Multiple Lambda Layers (dependencies + shared code)