Cloud Functions

"Serverless means someone else worries about the server — but you still worry about the code." — Unknown

TL;DR

Guides Cloud Functions for Firebase development — HTTP endpoints, Firestore document triggers, Auth event handlers, Storage upload triggers, and PubSub messaging. Covers TypeScript patterns, error handling, cold start optimization, and deployment strategies. Use when you need server-side logic in a Firebase project. [EXPLICIT]

Procedure

Step 1: Discover

• Identify server-side logic needs (data validation, aggregation, notifications, integrations)
• Check existing functions and their trigger types
• Review runtime configuration and environment variables
• Determine region requirements for latency optimization

Step 2: Analyze

• Categorize functions by trigger: HTTP (callable/request), Firestore (onCreate/onUpdate/onDelete), Auth (onCreate), Scheduled, PubSub
• Plan function organization (one file per domain vs feature folders)
• Evaluate cold start impact and optimization strategies
• Design error handling and retry behavior per trigger type

Step 3: Execute

• Set up Functions with TypeScript and firebase-functions/v2 API
• Implement HTTP callable functions with onCall for authenticated endpoints
• Create Firestore triggers for data denormalization and aggregation
• Add Auth triggers for user profile initialization on sign-up
• Configure scheduled functions with onSchedule for periodic tasks
• Set up proper error handling: HttpsError for callables, retry logic for background
• Use defineSecret for sensitive configuration (API keys, credentials)
• Deploy to specific regions for latency optimization

Step 4: Validate

• Test all functions locally with Firebase Emulator Suite
• Verify Firestore triggers handle idempotency (same event processed twice)
• Check function logs in Cloud Console for errors and performance
• Confirm deployment succeeds and functions respond correctly in staging

Quality Criteria

• All functions use TypeScript with strict typing
• HTTP callable functions validate input parameters and handle errors with HttpsError
• Background triggers are idempotent (safe to re-execute)
• Secrets stored via defineSecret, never hardcoded
• Evidence tags applied to all claims

Anti-Patterns

• Using functions.https.onRequest for authenticated endpoints instead of onCall
• Not handling cold starts (global scope initialization, lazy imports)
• Deploying all functions when only one changed (firebase deploy --only functions:specificFn)

Related Skills

• firebase-setup — Functions are initialized as part of Firebase project setup
• serverless-patterns — general serverless patterns apply to Cloud Functions

Usage

Example invocations:

• "/cloud-functions" — Run the full cloud functions workflow
• "cloud functions 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]

Edge Cases

Scenario	Handling
Empty or minimal input	Request clarification before proceeding
Conflicting requirements	Flag conflicts explicitly, propose resolution
Out-of-scope request	Redirect to appropriate skill or escalate