⚔️ Cloud Functions vs Cloud Run: When to Use What (2025 Guide)

If you're building on Google Cloud, two of the most common options for running backend code are:

• ✅Cloud Functions
• ✅Cloud Run

At Dezoko, we've used both across dozens of projects -- from small automations to high-traffic APIs and background workers.

But here's what most developers get wrong:

> You don't pick one because it's "newer" or "faster."

> You pick based on use case, control, cost, and scalability.

In this blog, we'll break down:

• When to use Cloud Functions
• When to use Cloud Run
• Performance, pricing, and cold-start comparisons
• Real-world architectures we've deployed

🚀 Quick Summary Table

🔧 When We Use Cloud Functions

Cloud Functions are ideal for:

• Event-driven logic

(e.g., Firebase Auth triggers, Firestore `onWrite`)

• Quick scripts / automations

(e.g., send email on signup)

• Minimal setup

(No Docker, no server management)

• Tightly integrated Firebase apps

• ✅Examples from our client work:

• Trigger email when user signs up (Firebase Auth + Mailchimp)
• Sync Firestore data to BigQuery on `onUpdate`
• Handle Stripe webhook for one-time purchase
• Auto-tag images with Cloud Vision on upload to GCS

🛠️ When We Use Cloud Run

Cloud Run is our go-to for:

• Public or private APIs
• Multi-route backends (Express, FastAPI, etc.)
• Worker services for queue processing
• Cron jobs via Cloud Scheduler + Pub/Sub
• Custom environments / Docker builds

• ✅Examples from our production apps:

• REST API for mobile app with Firebase Auth token verification
• AI document parser using OpenCV + Tesseract in Python container
• Cloud Tasks processor for PDF generation and email dispatch
• Server-side rendered (SSR) dashboard with authentication middleware
• On-demand GPT-powered report generation

💰 Pricing Comparison (Real-World)

🧠 TL;DR:

Cloud Functions is cheaper for *tiny, infrequent jobs*.

Cloud Run is cheaper for *high-traffic APIs* and *batch jobs*.

🔐 Security & IAM

We use:

• IAM roles per function / service
• JWT-based auth for APIs
• VPC connectors if database access is needed
• Cloud Armor + API Gateway for Cloud Run (if needed)

💬 What Clients Ask Us

> "Can we start with Cloud Functions and move to Cloud Run later?"

> Yes -- and we often do! Functions are great to validate logic. Cloud Run is best for scale.

> "Can I use both?"

> Absolutely. Many of our clients use Cloud Functions for Firebase logic + Cloud Run for APIs or heavy compute tasks.

🔄 Real Architecture We Use

[ Firebase Auth ]
       ↓
[ Frontend (Flutter / Nuxt) ] → [ Cloud Run API ]
                                         ↓
                       [ DB (Cloud SQL / Firestore) ]
                                         ↓
                [ Cloud Tasks / BigQuery / PubSub ]

[ Firebase Trigger ] → [ Cloud Function → Cloud Run ]

💼 Summary: Our Recommendation

📞 Need Help Picking or Migrating?

We offer:

• ✅Cloud Run / Cloud Function setup
• ✅Firebase integrations + migration
• ✅Secure API architecture
• ✅GCP billing optimization
• ✅Full-stack design + CI/CD