Api Gateway, multiple lambda in the same JAR

Question

I'm trying to deploy an API suite by using Api Gateway and implementing code in Java using lambda. Is it ok to have many ( related, of course ) lambdas in a single jar ( what I'm supposing to do ) or it is better to create a single jar for each lambda I want to deploy? ( this will became a mess very easily)

Answer 1

This is really a matter of taste but there are a few things you have to consider.

First of all there are limitations to how big a single Lambda upload can be (50MB at time of writing).
Second, there is also a limit to the total size of all all code that you upload (currently 1.5GB). These limitations may not be a problem for your use case but are good to be aware of.

The next thing you have to consider is where you want your overhead. Let's say you deploy a CRUD interface to a single Lambda and you pass an "action" parameter from API Gateway so that you know which operation you want to perform when you execute the Lambda function. This adds a slight overhead to your execution as you have to route the action to the appropriate operation. This is likely a very fast routing but nevertheless, it adds CPU cycles to your function execution.

On the other hand, deploying the same jar over several Lambda function will quickly get you closer to the limits I mentioned earlier and it also adds administrative overhead in managing your Lambda functions as that number grows. They can of course be managed via CloudFormation or cli scripts but it will still add an administrative overhead.

I wouldn't say there is a right and a wrong way to do this. Look at what you are trying to do, think about what you would need to manage the deployment and take it from there. If you get it wrong you can always start over with another approach.

Personally I like the very small service Lambdas that do internal routing and handles more than just a single operation but they are still very small and focused on a specific type of task be it a CRUD for a database table or managing a selected few very closely related operations.