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

App Engine is a fully managed platform for building scalable web apps with built-in services, while Cloud Run runs containerized apps with flexible scaling and more control over runtime. Choose App Engine for easy app deployment without managing infrastructure, and Cloud Run for container-based workloads needing custom environments.

Quick Comparison

Here is a quick side-by-side look at key factors between App Engine and Cloud Run.

Factor	App Engine	Cloud Run
Deployment	Deploy code directly or via supported runtimes	Deploy container images
Scaling	Automatic scaling with instance management	Automatic scaling based on requests, including to zero
Runtime Control	Limited to supported runtimes and versions	Full control with custom containers
Use Case	Web apps, APIs with standard runtimes	Any containerized workload, microservices
Pricing	Based on instance hours and resources	Based on CPU, memory, and request time
Infrastructure Management	Fully managed, no server management	Fully managed, but containerized environment

Key Differences

App Engine is designed as a platform-as-a-service (PaaS) that abstracts away infrastructure details. It supports specific programming languages and runtimes, letting you deploy code directly without worrying about containers or servers. It automatically handles scaling, load balancing, and health checks, making it ideal for developers who want simplicity and fast deployment.

Cloud Run is a serverless compute platform that runs any stateless container. It gives you full control over the runtime environment by letting you package your app and dependencies into a container image. Cloud Run scales automatically based on incoming traffic and can scale down to zero when idle, which can save costs. It is more flexible but requires container knowledge.

In summary, App Engine is best when you want a managed environment with minimal configuration and supported runtimes, while Cloud Run suits workloads needing custom environments or container portability.

Code Comparison

Here is a simple example of deploying a "Hello World" web app on App Engine using Python.

python

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return 'Hello, App Engine!'

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080)

Output

Hello, App Engine!

Cloud Run Equivalent

To run the same app on Cloud Run, you first create a Docker container. Here is a Dockerfile example for the same Python app.

dockerfile

FROM python:3.9-slim

WORKDIR /app

COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt

COPY . .

CMD ["python", "app.py"]

Output

Container image built and deployed to Cloud Run, serving 'Hello, App Engine!' on HTTP requests

When to Use Which

Choose App Engine when you want to quickly deploy web apps or APIs using supported languages without managing containers or infrastructure. It is great for standard web workloads and when you prefer a fully managed environment with minimal setup.

Choose Cloud Run when you need more control over your runtime environment, want to deploy any containerized app, or require flexible scaling including scaling to zero. It fits microservices, custom runtimes, and workloads that benefit from container portability.

Key Takeaways

App Engine is a fully managed PaaS for supported runtimes with simple deployment.

Cloud Run runs any containerized app with flexible scaling and full runtime control.

Use App Engine for quick web app deployment without container knowledge.

Use Cloud Run for custom environments, microservices, and container portability.

Both scale automatically, but Cloud Run can scale down to zero to save costs.