Using a Realtime Database keeps your app data synced instantly. This means your app listens for changes and updates UI right away. While this is great for user experience, it can use more battery and data because it keeps a live connection open. Frame rates stay smooth if you manage updates well, but too many rapid updates can cause UI lag. Memory use is usually low, but large data snapshots can increase it temporarily.
To keep your app smooth, limit the data you listen to. Use queries to get only what you need, not the whole database. Batch updates or debounce rapid changes to avoid too many UI refreshes. Use lightweight listeners and remove them when not needed. Also, update only the parts of UI that changed instead of re-rendering everything.
Adding Realtime Database libraries increases your app size moderately, usually a few megabytes. This can slightly increase startup time, especially on slower devices. To reduce impact, use only the parts of the SDK you need and enable code shrinking tools like ProGuard (Android) or Bitcode (iOS). Lazy load database features if possible to speed up initial load.
On iOS, Realtime Database uses native sockets managed by Firebase SDK with background modes support for limited background syncing. On Android, it uses persistent connections with automatic reconnection and offline caching. Android devices may handle network changes more aggressively. Both platforms require proper permissions for network access. iOS apps need to handle App Transport Security (ATS) rules for secure connections.
It is likely your app is loading too much data from the Realtime Database at once or listening to large data sets without filtering. This causes slow startup and UI delays. To fix this, query only the needed data, add indexes in your database, and remove unnecessary listeners during screen load.