I am designing a serverless application with AWS Lambda. There’s a piece of code on one of the functions that process the request in a certain way. I am going to make another function that’s going to make the same processing with the request data, in the same way.

The problem is that, if I change the processing function in one of the Lambda functions, I’m going to have to copy the function and paste it into the other Lambda function. Every time I make a change I will have to do this. This will be even more cumbersome if I want to do the same processing function in more than two Lambda functions.

Is there a way to share pieces of code between Lambda functions, so I may respect DRY principles? Thanks.

Now you can use Layers to share libraries and code between your Functions.
It is possible to base more then one Function on one Layer.

You can create a zip file for the Layer pretty much the same way as you can do so for a Function. The only thing will be that all the common packages go to python/lib/python3.7/site-packages directory inside of zip and all your code goes to python directory.

So if you have file structure like this:

Then from your Lambda Function’s code you can reference it like this: