Reproduction steps:

1. clone the repo
2. cd functions
3. npm install

TO Test

4. npm run serve
5. hit the function endpoint http://localhost:5099/fbdb-test-001/us-central1/helloWorld

You should see the following error appear in your console @firebase/database: FIREBASE WARNING: wss:// URL used, but browser isn't known to support websockets. Trying anyway.

And if you wait long enough (1 min should be default) you will see the function timeout

To Fix

6. add "@firebase/database-compat": "0.1.2" the dependency node in functions/package.json
7. run npm i
8. Go back to step 4

You should now see the execution without errors