Firebase Authentication adds network calls to your app for user sign-in and token refresh. These calls can cause slight delays but usually do not affect frame rate if handled asynchronously. Memory usage is minimal, mostly for storing user session data. Battery impact is low since authentication happens infrequently, typically at app start or user action.
Use asynchronous calls with Kotlin coroutines or callbacks to avoid blocking the main thread. Cache user credentials securely to reduce repeated sign-ins. Avoid heavy UI updates during authentication. Show simple loading indicators to keep UI responsive. Use Firebase's built-in token refresh to maintain session without user interruption.
Adding Firebase Authentication increases your app size by about 2-5MB depending on dependencies. This is moderate and acceptable for most apps. Startup time impact is minimal if authentication is done after initial UI loads. Use ProGuard or R8 to shrink unused Firebase code and reduce size.
Both platforms use Firebase SDKs but with platform-specific APIs (Swift for iOS, Kotlin for Android). iOS requires configuring GoogleService-Info.plist, Android uses google-services.json. iOS apps must handle Sign in with Apple if used, Android handles Google Sign-In differently. Both require proper OAuth client setup in Firebase Console.
Likely your app is performing Firebase Authentication synchronously on the main thread, blocking UI rendering. Or you may be waiting for network calls without showing progress. To fix, move authentication calls off the main thread, use asynchronous patterns, and show a loading indicator to keep UI responsive.