100 — Firebase Cost Optimization {Performance}

Purpose

Minimize Firebase operational costs while maintaining application performance. Reduce Firestore reads/writes through efficient query patterns, mitigate Cloud Functions cold starts, and implement storage lifecycle management. [EXPLICIT]

Physics — 3 Immutable Laws

1. Law of Read Reduction: Every Firestore read costs money. Cache aggressively, paginate always, denormalize strategically. Never read more documents than displayed. [EXPLICIT]
2. Law of Function Efficiency: Cloud Functions bill per invocation and compute time. Minimize cold starts, reduce execution duration, avoid unnecessary triggers. [EXPLICIT]
3. Law of Storage Hygiene: Unused files in Firebase Storage cost money monthly. Lifecycle rules delete temp files. User-uploaded originals are cleaned after processing. [EXPLICIT]

Protocol

Phase 1 — Firestore Optimization

1. Pagination: Every list query uses limit() + cursor-based pagination (startAfter). Never getDocs() without limit. [EXPLICIT]
2. Caching: Enable Firestore persistence (enablePersistence()). Use getDocFromCache() before getDocFromServer(). [EXPLICIT]
3. Denormalization: Store computed/aggregated data to avoid multi-document reads. Update via Cloud Function triggers. [EXPLICIT]
4. Composite queries: Replace multiple queries with composite indexes. Use in operator for batch lookups (max 30 values). [EXPLICIT]
5. Listener management: onSnapshot unsubscribe on component unmount. No orphan listeners. [EXPLICIT]

Phase 2 — Cloud Functions Optimization

1. Min instances: Set minInstances: 1 for critical functions to eliminate cold starts. [EXPLICIT]
2. Lazy imports: Import heavy SDKs inside function body, not at module top level. [EXPLICIT]
3. Regional deployment: Deploy functions in same region as Firestore to reduce latency and egress. [EXPLICIT]
4. Batch triggers: Use onWrite batch processing instead of individual onCreate for bulk operations. [EXPLICIT]
5. Timeout/memory: Right-size function memory (128MB default). Set timeout to actual max expected + 20%. [EXPLICIT]

Phase 3 — Storage & Billing Controls

1. Lifecycle rules: Auto-delete temp files after 7 days via Cloud Storage lifecycle policy. [EXPLICIT]
2. Image cleanup: Delete original after resize extension processes it (keep resized only). [EXPLICIT]
3. Billing alerts: Set alerts at 50%, 80%, 100% of monthly budget in Google Cloud Console. [EXPLICIT]
4. Budget cap: Configure billing budget with auto-disable for non-production projects. [EXPLICIT]

I/O

Input	Output
Firestore query patterns	Optimized queries with pagination + caching
Cloud Functions config	Right-sized memory, timeout, min instances
Storage file inventory	Lifecycle rules for auto-cleanup
Monthly budget	Billing alerts and caps configured

Quality Gates — 5 Checks

1. Every query has limit() — no unbounded reads. [EXPLICIT]
2. Firestore persistence enabled — offline cache active on client. [EXPLICIT]
3. Min instances set for critical functions — cold start < 500ms. [EXPLICIT]
4. Billing alerts at 50%, 80%, 100% — configured in Cloud Console. [EXPLICIT]
5. Storage lifecycle active — temp files auto-deleted after 7 days. [EXPLICIT]

Edge Cases

• Firestore listener explosion: Shared state via context — one listener per collection, not per component.
• Functions concurrency: Gen2 functions support concurrency. Set concurrency: 80 to reduce instance count.
• Spark plan limits: Free tier has 50K reads/day, 20K writes/day. Monitor to avoid hard limit.
• Egress costs: Firestore egress is free within same region. Cross-region reads incur egress charges.

Self-Correction Triggers

• Billing exceeds 80% of budget → audit top cost drivers in Cloud Console.
• Firestore reads > 50K/day → review queries, add caching, increase denormalization.
• Functions cold start > 2s → add min instances, reduce imports, check memory allocation.
• Storage costs growing → run file inventory, verify lifecycle rules, delete unused assets.

Usage

Example invocations:

• "/firebase-cost-optimization" — Run the full firebase cost optimization workflow
• "firebase cost optimization on this project" — Apply to current context

Assumptions & Limits

• Assumes access to project artifacts (code, docs, configs) [EXPLICIT]
• Requires English-language output unless otherwise specified [EXPLICIT]
• Does not replace domain expert judgment for final decisions [EXPLICIT]