Ive regretted 99% of the services Ive built in AWS lambda over the years. Everytime it gets more complex than a couple hundred lines of code over a few lambas I start to think “if this were just one service, development, deployments, cicd, testing, storage would all be simpler”.

My deployments to Lambda are extremely simple. All I do is hit save in VSCode and the Lambda is updated. Change the env to prod and it deploys instantly to prod.

There's tools that make it easy, I'm still using a tool I built 10 years ago. Very little has changed except the addition of layers, which are also pretty easy and automatically handled in my dev tool.

All the Lambdas I write also run locally, and testing isn't an issue.

The only gripe I have with Lambda is when they deprecate older nodejs versions, and I am forced to update some of my Lambdas to run on current nodejs, which then leads to refactoring due to node module incompatibilities in some specific situations. But those are really nodejs problems and not so much Lambda problems, and it does get me to keep my apps updated.

YMMV.

I inherited a Lambda application at one job - when I started it was probably 200+ Lambdas and it got to 128 Lambdas. Lots of message queues, lots of Lambdas subscribed to queues where they ignored 99% of incoming messages... quite a mess. The Lambdas that are gone got repackaged into a SpringBoot application which thoroughly simplified things.