Local development tooling
Similar to AWS SAM (https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-using-invoke.html) or Google Cloud Functions Framework (https://cloud.google.com/functions/docs/functions-framework).
I.e. the ability to run functions locally. It's expensive and slow to have to run and test code in a project remotely all the time even for small changes.
+1 The number one reason I keep choosing to not use MongoDB Realm to build my apps is the lack of local tooling. I cringe at the idea of coding and testing functions remotely via the browser. Once Realm catches up with the rest of the world on this feature I'll gladly use it for my projects.
+1 Realm is not a developer friendly environment
I have some calculation intensive functions I've been trying to test and it has been painful trying to optimise them for performance. Not being able to see the logs until the function finishes is frustrating, especially if the function then errors and I don't get to see any of the logs! Maybe someone would like to write an extension for VS code that simulates the MongoDB Realm environment?
Matt Price commented
+ 1 for this. Testing and developing functions is a real time killer. We've also found that once you deploy a function, it takes time to propagate so multiple calls to the function are required to see the change.
Not only for functions, but also please consider local tooling for graphql.
AWS Amplify has a local development feature which is really useful. Just run a simple command `amplify mock api` then you get a locally running graphql endpoint. It really speeds up both development and testing.