aws-lambda-runtime-interface-emulator VS up

Enter the aws-lambda-runtime-interface-emulator. This tool will allow us to emulate the AWS Lambda Runtime API locally (I suspect that the AWS SAM uses this tool under the hood as well). The aws-lambda-runtime-interface-emulator is designed to be used with Docker. Still, nothing stops us from containerizing our code for the sake of development and then, whenever we are ready, proceeding with deployment how we wish to. This local workflow is a bit more involved than the previous one, but it might be a valid alternative for those not using AWS SAM or are already using containers to deploy their Lambdas.

There is a special tool to test AWS Lambda images locally. It's called AWS Lambda Runtime Interface Emulator (RIE). You have two options: include RIE in your image or install it locally. We don't need it in the production image, so let's choose the second option. We will download binary locally and mount it to our image if we need to test it.

Suggestions:

1. If you are building APIs and using Lambda functions as targets from an API Gateway API, look into libraries like serverless-wsgi (Python) or wai-handler-hal (Haskell) that translate between API Gateway request/response payloads and some kind of ecosystem-native representation. Then as long as you're writing code where all state gets persisted outside of the request/response cycle, you can develop locally as if you were writing for a more normal deploy environment.

2. Look into the lambda runtime interface emulator ( https://github.com/aws/aws-lambda-runtime-interface-emulator... ). This lets you send invoke requests to a fake listener and locally test the lambda more easily. While the emulator is provided in the AWS container base images, you don't need to run it inside a container if you're deploying with zip files. (AWS-provided container images automatically enable the emulator if not running in a lambda runtime environment, and using docker for port remapping is nice. But not at all required.)

3. Get really good at capturing all requests to external services, and mocking them out for local testing. Whether this is with free monads, effect systems, gateway classes will depend on your language and library choices.

Apex is an open-source tool that makes it easy to build and deploy serverless applications on AWS. It's a great tool for any serverless developer, as it simplifies the process of building and deploying serverless applications, making it easier to focus on writing code.

I can also recommend serverless.com framework for local development and running lambdas offline.

AWS provides a docker image for emulating DynamoDB which works great for local dev and will commonly be paired with lambdas.

Another option I have used recently for implementing node web services is https://github.com/apex/up which also has a nice local dev experience.

Projects: apex/up, git-extras, koajs/koa, clibs/clib, commander.js