Upgrading Your AWS Lambdas to Node 20

The Node 16 runtime on Lambda will be deprecated in June.

Upgrading to Node 18 or 20 is relatively easy for most applications, with few breaking changes from Node 16.

Some notable additions are the native support for fetch(), which you might be familiar with from browser environments, and a built-in test runner.

What is more difficult, is the lack of the AWS SDK v2, which is included out of the box in the node16.x Lambda runtime, but not in the more recent runtime versions.

Upgrading to AWS SDK v3

Ideally, you'd upgrade to v3 of the SDK, but this might involve rewriting a lot of your code. If you want to go this route, the codemod is a good starting point.

Including v2 in your bundle

For those of us not ready to move on to v3 yet, you need to include v2 in your bundle.

With serverless

If you use the Serverless framework, you might need to move the aws-sdk package from devDependencies to dependencies in your package.json. This will tell the framework to not exclude it from the bundle.

With serverless-esbuild

The serverless-esbuild plugin by default will exclude the aws-sdk package as well, so you need to specifically pass an empty array to override this behaviour:

provider:
   runtime: nodejs20.x

custom:
   serverless-esbuild:
      exclude: []

This will tell esbuild to bundle the aws-sdk. The AWS SDK v2 is massive though, so this might result in large bundles, or even hang esbuild if it can't use enough memory.

This is a problem we've experienced with several of our larger services, and there's two good strategies for getting around it:

• Manually including the SDK in the package by adding node_modules/aws-sdk/** into your package patterns. This leads to a relatively large package (multiple MBs), but is pretty quick. You can further optimise this by excluding files in the SDK folder that you don't need, like the dist folder or all of the *.d.ts definition files.
• If you want to keep your lambda package very small, an alternative solution is including the SDK as a Lambda Layer. You can create this layer by zipping op the SDK (ensure to keep the folder structure, so that it ends up in node_modules).