Fix Firebase high read count from real-time listeners

Problem: React Native Firebase app has extremely high read counts despite having many server-side functions. Read costs are skyrocketing.

Root cause: High Firebase reads are caused by client-side listening patterns (onSnapshot), not server functions.

Fix 1 - Replace real-time listeners with one-time fetches:

// ❌ Bad - Real-time listener re-reads on every change
onSnapshot(collection(db, 'users'), (snapshot) => {
  setUsers(snapshot.docs.map(d => d.data()));
});

// ✅ Good - One-time fetch
const snapshot = await getDocs(collection(db, 'users'));
setUsers(snapshot.docs.map(d => d.data()));

Fix 2 - Always use where(), limit(), pagination:

getDocs(query(
  collection(db, 'products'),
  where('category', '==', 'electronics'),
  limit(20)
))

Fix 3 - Enable offline persistence:

enableIndexedDbPersistence(db);

Fix 4 - Precompute aggregations with Cloud Functions.

Fix 5 - Check component re-mounting. Use React.memo, useMemo, or state management.

Source: https://www.reddit.com/r/Firebase/comments/1qmcmkf/database_read_count_and_performance_issues/