Firebase Phone Auth is widely used, then teams hit SMS quotas, billing surprises, SHA configuration issues, and codes that never arrive on Egyptian numbers. Those are product problems, not a reason to abandon the rest of Firebase.
Common Firebase OTP problems
- SMS not delivered on local operators despite a valid number.
- Quota or billing blocks after leaving the free tier.
- Android SHA fingerprints missing for the Play signing key.
- Users stuck on the code screen with no fallback.
Replace phone auth, not the whole stack
You can keep Firebase Analytics, Crashlytics, or Cloud Messaging and still move phone verification to a missed-call provider. Shernova does not replace your user database. It verifies the phone, then your backend continues the session.
What changes in the app
You remove the SMS code UI and call a verification session instead. Users see a number to call, then return to the app. Details are in Migrate from Firebase / SMS OTP.
Do not share secret API keys in the mobile app. Use a publishable key on the device and keep secret keys on your server, the same rule you already follow with other providers.
Next step for developers
Shernova is a phone-verification layer for your app, not an end-user consumer app. Create a developer account, follow the quick start, then test the flow from the dashboard.