Cloud Run vs App Engine: Key Differences and When to Use Each

Cloud Run is a serverless platform that runs containers and offers flexible scaling with full control over the runtime environment. App Engine is a fully managed platform for deploying apps with built-in services and automatic scaling but less control over the environment.

Quick Comparison

This table summarizes the main differences between Cloud Run and App Engine across key factors.

Factor	Cloud Run	App Engine
Deployment Unit	Container images	Source code or prebuilt runtimes
Runtime Control	Full control over container environment	Limited to supported runtimes and versions
Scaling	Automatic, scales to zero and up quickly	Automatic, scales to zero and up with some delay
Supported Languages	Any language via container	Limited to supported languages (Java, Python, Go, Node.js, etc.)
Use Case	Microservices, custom runtimes, flexible workloads	Standard web apps, APIs with built-in services
Pricing Model	Pay per request and CPU/Memory usage	Pay per instance hour and usage

Key Differences

Cloud Run runs your app inside containers, giving you full control over the runtime, libraries, and environment. You package your app as a container image and deploy it, so you can use any language or framework. It scales automatically from zero to many instances based on traffic, making it great for microservices or apps needing custom setups.

App Engine offers a more managed experience where you deploy source code or use supported runtimes. It handles most infrastructure details for you, including scaling and load balancing, but you have less control over the environment. It is ideal for standard web apps or APIs that fit within its supported languages and services.

In summary, choose Cloud Run if you want flexibility and control with containerized apps, and choose App Engine if you want a simple, fully managed platform for common web applications without managing containers.

Code Comparison

Here is an example of deploying a simple HTTP server using Cloud Run with a Dockerfile and Node.js.

javascript

const express = require('express');
const app = express();
const port = process.env.PORT || 8080;

app.get('/', (req, res) => {
  res.send('Hello from Cloud Run!');
});

app.listen(port, () => {
  console.log(`Server listening on port ${port}`);
});

Output

Server listening on port 8080

App Engine Equivalent

This is the equivalent simple HTTP server using App Engine Standard Environment with Node.js.

javascript

const express = require('express');
const app = express();
const port = process.env.PORT || 8080;

app.get('/', (req, res) => {
  res.send('Hello from App Engine!');
});

app.listen(port, () => {
  console.log(`Server listening on port ${port}`);
});

Output

Server listening on port 8080

When to Use Which

Choose Cloud Run when: you need full control over your app environment, want to deploy any language or framework using containers, or require fast scaling for microservices.

Choose App Engine when: you prefer a fully managed platform with minimal setup, your app fits supported runtimes, and you want built-in services like traffic splitting and versioning.

Key Takeaways

Cloud Run runs containerized apps with full environment control and flexible scaling.

App Engine offers a fully managed platform with limited runtime choices but simpler deployment.

Use Cloud Run for custom runtimes and microservices; use App Engine for standard web apps.

Both scale automatically, but Cloud Run scales faster and supports any language via containers.

Pricing differs: Cloud Run charges per request and resource use; App Engine charges per instance.