How does Firestore pricing work?

Firestore pricing (as of 2024): (1) Document reads — $0.06 per 100,000 reads. Each getDoc() and each document in a query result counts as one read. Real-time listeners charge one read on initial load plus one read per change notification per listening client; (2) Document writes — $0.18 per 100,000 writes (set, add, update, delete each count as one); (3) Document deletes — $0.02 per 100,000 deletes; (4) Stored data — $0.108 per GB/month; (5) Network — free within Google Cloud; egress to internet varies by region. Free tier (Spark plan) includes 50,000 reads, 20,000 writes, 20,000 deletes/day, 1GB storage, 10GB/month network egress. Cost optimization strategies: minimize real-time listeners (use one-time fetches when real-time isn't needed), paginate large queries to avoid fetching unused documents, cache data client-side, batch writes (doesn't reduce write count but reduces network requests), use aggregation queries (COUNT, SUM, AVG — charged as 1 read regardless of matching documents).