App Engine Standard & Flexible

Google App Engine is the original serverless platform on Google Cloud, predating both Cloud Functions and Cloud Run. It remains a powerful option for deploying web applications and APIs with zero infrastructure management. App Engine offers two environments: Standard and Flexible, each with distinct characteristics and trade-offs.

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What Is App Engine?

App Engine is a fully managed Platform-as-a-Service (PaaS) that lets you build and deploy applications without managing the underlying infrastructure. You write code, define your configuration in an app.yaml file, and deploy. Google handles scaling, load balancing, health checks, patching, and monitoring.

Key Features

Feature	Description
Fully managed	No servers or clusters to manage
Auto-scaling	Scales based on incoming traffic
Built-in services	Memcache, Task Queues, Cron, Identity-Aware Proxy
Versioning	Deploy multiple versions and split traffic between them
Custom domains	Map your own domain with managed SSL certificates
Zero downtime deploys	Traffic splitting ensures smooth rollouts

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Standard Environment

The Standard environment runs your application in a secure sandbox. It is optimised for rapid scaling, including scaling to zero, and offers a generous free tier.

Supported Runtimes

Runtime	Versions
Python	3.8, 3.9, 3.10, 3.11, 3.12
Java	11, 17, 21
Node.js	18, 20
Go	1.21, 1.22
PHP	8.1, 8.2, 8.3
Ruby	3.2, 3.3

Standard Environment Characteristics

Characteristic	Detail
Scaling	Scales to zero — no charges when idle
Startup time	Seconds (fast cold start)
Instance classes	Predefined (F1, F2, F4, F4_1G)
Max request timeout	10 minutes
Local disk	In-memory only (no persistent local storage)
Sandbox	Restricted environment — limited system calls

# app.yaml for Standard environment
runtime: python312
instance_class: F2
automatic_scaling:
  min_instances: 0
  max_instances: 10
  target_cpu_utilization: 0.65
env_variables:
  DATABASE_URL: "your-connection-string"

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Flexible Environment

The Flexible environment runs your application in Docker containers on Compute Engine VMs. It offers more customisation — you can use any runtime, install native libraries, and write to local disk.

Flexible Environment Characteristics