Using Git with a Frontend and Backend Gateway

I've previously used the dev, test, and prod workflow using Git based off the Deployment Best Practices guide.

We've hit a point where we have about 60 perspective clients connected at any given time with usage spikes above that. We are wanting to split out the front-end and back-end for performance. My understanding is the back-end will handle all the tags and the front-end will use remote tags from the back-end.

I'm unsure how best to integrate this Gateway architecture with Git.
Is it best to have two separate repos?
Or one repo and disable functionality for each gateway?

For the dev environment, do you also have a front-end and back-end Gateway or can you develop on a single gateway then split the resources apart on the test and prod front and back-ends?

I would definitely have two repos. Or if you really want, a monorepo with each whole gateway's configuration "nested" below it.

That is, something like:

someSetup/
    backup/
        config/
        projects/
    frontend/
        config/
        projects/

The advantage of the monorepo in this case being that it's easy to update any shared config via a commit to both places.
The disadvantage being that it's more awkward to pull in a subset of a repo via git operations, though still possible.

Blegh! Don't do this!