Shameless plug - my co-founder and I are working on a somewhat similar tool called [Foundry](https://foundryapp.co). It automatically creates a development environment for you that is a copy of your production environment. You also get access to a copy of your production data and real-time feedback through our REPL tool - we evaluate your code every time you save a file and send you back the output.

So far we support Firebase and their Firestore, RealtimeDB, and Cloud Functions. In action, the development with Foundry looks like this:

- (1) Start Foundry session in your terminal

- (2) Specify a slice of your production Firestore/RealtimeDB we should copy for you

- (3) Specify what Cloud Functions we should trigger for you and with what data

- (4) Every time you save your code we trigger those functions as you specified and send you back the output

Every development environment is created for each developer separately on the fly (it takes less than 30seconds to have your environment ready). You don't have to wait minutes for your Cloud Functions to get deployed. You get a response usually in just a few seconds.

We are also working on a new feature that will make it possible to have one "master" always-online environment that is publicly accessible.