We use AWS lambda for running slower background tasks triggered from a user action on a website (eg. generating a report, clearing and rebuilding a cache, etc...).

We deploy our full monolithic app to lambda (as a docker image) and then just have a wrapper entrypoint script that dispatches the request to the appropriate module and function.

There are benefits to keeping each lambda function small but we like the benefit of deploying one lambda and being able to call any function within the monolith.