Hi, Stewart here from the Firebase team.

We released a C++ API for the Realtime Database earlier today targeting iOS and Android, you can get started with it here https://firebase.google.com/docs/database/cpp/start

Using the C++ API within Unreal (assuming you're targeting mobile) is a little tricky as we have dependencies upon Android resources (e.g AARs) that can be hard to integrate into Unreal's build system. You would probably need to list the set of transitive dependencies (see https://groups.google.com/d/msg/firebase-talk/15SdQA8xtnc/aw...).

It would be informative for us to understand which platforms you're targeting and which features of Firebase (we support more than the Realtime Database) you would consider using.

Cheers, Stewart