Standard vs Flexible Environments

Comparing App Engine Standard and Flexible environments — feature differences, pricing, and how to choose the right one for your workload.

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Two Environments

App Engine offers two execution environments. They share the same API and workflow but differ significantly in how your code runs, what you can do, and what you pay.

Aspect	Standard	Flexible
Infrastructure	Sandboxed containers in a managed runtime	Docker containers on Compute Engine VMs
Scale to zero	Yes — no traffic means no instances, no cost	No — minimum 1 instance always running
Instance startup	Seconds (milliseconds for warm instances)	Minutes (VM provisioning + container build)
Deployment time	Seconds	5-15 minutes
Max request timeout	10 minutes (HTTP/task queue)	60 minutes
Scaling types	Automatic, Basic, Manual	Automatic, Manual
WebSockets	No	Yes
Local disk	Only /tmp (read/write)	Full ephemeral disk
Background processes	No	Yes
SSH debugging	No	Yes
Custom runtimes	No — supported runtimes only	Yes — any language via Dockerfile
Free tier	Yes	No
Pricing basis	Instance-hours	vCPU, memory, persistent disk

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Standard Environment

The Standard environment runs your code in a sandboxed container using pre-configured runtimes. Instances start in seconds, and the environment can scale to zero when there’s no traffic.

What you get

• Fast deployments — your app is live in seconds
• Scales to zero — no traffic means no running instances and no cost
• Generous free tier — 28 instance-hours/day for F1 class
• Simple pricing — pay per instance-hour

Constraints

• Only supported runtimes (no custom languages)
• No WebSockets
• No background processes
• Filesystem read/write limited to /tmp
• Max request timeout of 10 minutes
• Cannot modify the runtime environment

When to use Standard

• Web applications and APIs
• Mobile backends
• Event-driven processing (Pub/Sub subscribers)
• Rapid prototyping and MVPs
• Applications with variable or unpredictable traffic
• Anything that fits within the supported runtimes

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Flexible Environment

The Flexible environment runs your code inside Docker containers on Compute Engine VMs. You get full control over the runtime, and can even bring your own Dockerfile for unsupported languages.

What you get

• Custom runtimes — any language via Dockerfile
• WebSockets — real-time communication support
• Background processes — run workers alongside your app
• Full disk access — ephemeral storage available
• SSH access — debug running instances
• Long-running requests — up to 60-minute timeout
• VPC access — connect to private resources

Constraints

• Minimum 1 instance always running (does not scale to zero)
• Deployment takes 5-15 minutes
• No free tier; at least one instance keeps running and accrues cost
• Pricing is based on vCPU, memory, and persistent disk
• More operational complexity than Standard

When to use Flexible

• Custom runtimes (.NET, Rust, Elixir, or any language)
• WebSocket-heavy apps (real-time chat, streaming)
• Long-running request processing (ML inference, video processing)
• Applications needing VPC access to private resources
• Workloads needing more than 1 GB memory per instance
• Applications requiring SSH debugging

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Supported Runtimes

Language	Standard	Flexible
Python	3.7 - 3.12	Yes
Java	8, 11, 17, 21	Yes
Go	1.12 - 1.22	Yes
Node.js	12 - 20	Yes
PHP	7.4 - 8.3	Yes
Ruby	2.7 - 3.2	Yes
Custom (any language)	No	Yes (via Dockerfile)

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Pricing Comparison

As of May 2026, these USD prices reflect the us-central1 rates on Google Cloud’s App Engine pricing page. Check the pricing page for your region and currency.

Standard Environment

Instance Class	Memory	CPU	Free Tier	Price/Hour
F1	128 MB	600 MHz	28 hr/day	$0.05
F2	256 MB	1.2 GHz	28 hr/day	$0.10
F4	512 MB	2.4 GHz	28 hr/day	$0.20
F4_1G	1024 MB	2.4 GHz	28 hr/day	$0.30
B1 (basic/manual)	128 MB	600 MHz	9 hr/day	$0.05
B2 (basic/manual)	256 MB	1.2 GHz	9 hr/day	$0.10
B4 (basic/manual)	512 MB	2.4 GHz	9 hr/day	$0.20
B8 (basic/manual)	1024 MB	4.8 GHz	9 hr/day	$0.40

Note: F-class instances are for automatic scaling. B-class instances are for basic and manual scaling.

Flexible Environment

Resource	Price
vCPU	$0.0526/hour
Memory	$0.0071/GiB-hour
Persistent disk	Compute Engine PD rates
Outbound network	Compute Engine rates

Warning: The Flexible environment has no free tier. Because it cannot scale below one running instance, a small configuration can accrue ongoing monthly cost even with little traffic.

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Decision Flowchart

flowchart TD
    Start["Choosing App Engine Environment"] --> Q1{"Do you need a custom<br/>runtime or Dockerfile?"}
    Q1 -->|Yes| Flex["Flexible Environment"]
    Q1 -->|No| Q2{"Do you need WebSockets<br/>or background processes?"}
    Q2 -->|Yes| Flex
    Q2 -->|No| Q3{"Do you need requests<br/>longer than 10 minutes?"}
    Q3 -->|Yes| Flex
    Q3 -->|No| Std["Standard Environment"]

Tip: Start with Standard unless you can name a specific feature that requires Flexible. You can mix both environments in the same application across different services.

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Using Both Environments Together

You can run Standard and Flexible services in the same application:

my-app/
  default-service/       # Standard (Python) — web frontend
    app.yaml
    main.py
  worker-service/        # Flexible (custom) — background processing
    app.yaml
    Dockerfile
  dispatch.yaml          # Routes requests between services

This lets you use Standard for cost-sensitive web serving and Flexible for workloads that need it.

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TL;DR

• Standard: sandboxed, fast deployments, scales to zero, free tier, limited to supported runtimes.
• Flexible: Docker containers, custom runtimes, WebSockets, background processes, no free tier.
• Start with Standard unless you need Flexible-specific features.
• You can use both environments in the same app across different services.
• As of May 2026, Standard instance pricing for common F/B classes is $0.05-$0.40/hour after the free tier. Flexible has no free tier and bills for vCPU, memory, disk, and network.

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Resources

Choose an App Engine Environment Official comparison of Standard and Flexible environments.

App Engine Pricing Detailed pricing for both environments including free tier.

App Engine Standard Documentation Documentation specific to the Standard environment.

App Engine Flexible Documentation Documentation specific to the Flexible environment.

App Engine Overview Getting started with App Engine.

Core Components Instances, services, versions, and routing.