The short answer to this quest, is you can’t access logs but you can profile your app in realtime. There’s no way for developers to look back and see where connections came from. As for the amount of traffic over time, you more-or-less just have to trust the Firebase usage graph, but should you?

I recently contacted Firebase Customer Support about maxed out simultaneous connections on a project that’s in development and has just one developer - me - working on it. What’s a simultaneous database connection?

“A simultaneous connection is equivalent to one mobile device, browser tab, or server app connected to the database.”

Well, working on one device, and opening one (or max two) browser tabs, I’ve recorded up to 100 connections, which is the hard limit permitted on the free (Spark) plan. Where are these connections coming from?

A friendly reply from Firebase Customer Support pointed me to the FAQs and how to profile your database using the Firebase database profiler.

The profiler captures realtime data on connected clients. In my case - using the --raw flag - it showed a single connecting device, along with the expected concurrent-disconnect and concurrent-connect events on page refresh.

For a while, the issue seemed to have resolved on its own, but now those lofty peaks are back (note that, for some reason, Firebase omits plotting zero values in the usage graph, which can be confusing). Some of the ‘busier’ days, I wasn’t even online, e.g., 31 October was the day I looked after my niece and nephew from dawn until the witching hours:

Firebase Usage Graph Showing Simultaneous Connections Over Time

The allure of serverless architecture is strong - Firebase promises everything from a realtime database to simple authentication without server-side code to cloud functions, and all these services are accessible via a single API - but have I chopped off an old reliable limb to scratch an itch? Right now, the usage graph is quiet again, but I’ve no idea how to further investigate the mystery of the manifold connections that arrive like crop circles, and it’s driving me nutty. Please leave helpful comments below!