Q:

How to install dependencies of lambda functions upon cdk build with AWS CDK

When using AWS SAM I used to run build command which would go through all of my Lambda function packages and install their dependencies (run npm install on them).
How can I achieve the same behavior with AWS CDK? It doesn't seem to do it automatically, or am I missing something?

A:

This functionality really is missing. You'll need to write your own packaging. Keep in mind that lambda dependencies must be built on a system with the same architecture as the target system in AWS (Linux) if any of the dependencies (such as Numpy) uses a shared library with native C code.
There's a Docker image available which aims to provide an environment as close to AWS as possible: lambci/lambda:build-python3.7
So if you're building on any non-Linux architecture, you might need this for some more complex lambda functions.
EDIT: I opensourced my Python code for lambda packaging: https://gitlab.com/josef.stach/aws-cdk-lambda-asset

