Choosing an App Engine Environment

You can run your applications in App Engine using the flexible environment or standard environment. You can also choose to simultaneously use both environments for your application and allow your services to take advantage of each environment's individual benefits.

Choosing your App Engine environment

Structuring your applications by using a microservice architecture aligns best with App Engine, especially if you decide to utilize both environments. There are several factors to consider when determining which environment is better suited to your application and it's services. Use the following sections to learn and understand which environment best meets your application's needs.

When to choose the flexible environment

Using the App Engine flexible environment means that your application instances run within Docker containers on Google Compute Engine virtual machines (VMs).

Generally, applications that receive consistent traffic, experience regular traffic fluctuations, or meet the parameters for scaling up and down gradually, are more cost effective in the flexible environment.

The flexible environment is optimal for applications with the following characteristics:

  • Source code that is written in a version of any of the supported programming languages:
    Python, Java, Node.js, Go, Ruby, PHP, or .NET
  • Runs in a Docker container that includes a custom runtime or source code written in other programming languages.
  • Depends on other software, including operating system packages such as imagemagick, ffmpeg, libgit2, or others through apt-get.
  • Uses or depends on frameworks that include native code.
  • Accesses the resources or services of your Cloud Platform project that reside in the Compute Engine network.

When to choose the standard environment

Using the App Engine standard environment means that your application instances run in a specialized sandbox, using the runtime environment of a supported language listed below.

Generally, building an application to run in the standard environment is more constrained and involved, but that also means that in some scenarios, your applications can achieve faster scale up times.

The standard environment is optimal for applications with the following characteristics:

  • Source code is written in specific versions of the supported programming languages:
    • Python 2.7
    • Java 7
    • PHP 5.5
    • Go 1.6
  • Intended to run for free or at very low cost, where you pay only for what you need and when you need it. For example, your application can scale to 0 instances when there is no traffic.
  • Experiences sudden and extreme spikes of traffic which require immediate scaling.

Comparing high-level features

The following table summarizes the differences between the two environments:

Feature Flexible environment Standard environment
Instance startup time Minutes Milliseconds
Maximum request timeout 60 minutes 60 seconds
Background threads Yes Yes, with restrictions
Background processes Yes No
SSH debugging Yes No
Scaling Manual, Automatic Manual, Basic, Automatic
Writing to local disk Yes, ephemeral (disk initialized on each VM startup) No
Modifying the runtime Yes (through Dockerfile) No
Automatic in-place security patches Yes (excludes container image runtime) Yes
Network access Yes Only via App Engine services (includes outbound sockets)
Supports installing third-party binaries Yes No
Location North America or Asia Pacific. The flexible environment is not supported in Europe. North America, Asia Pacific, or Europe
Pricing Based on usage of vCPU, memory, and persistent disks Based on instance hours

For an in-depth comparison of the environments, see the guide for your language: Python, Java, Go, or PHP.

Comparing the flexible environment to Compute Engine

While the flexible environment runs services in instances on Compute Engine VMs, the flexible environment differs from Compute Engine in the following ways:

  • The VM instances used in the flexible environment are restarted on a weekly basis. During restarts, Google's management services apply any necessary operating system and security updates.

  • You always have root access to Compute Engine VM instances. By default, SSH access to the VM instances in the flexible environment is disabled. If you choose, you can enable root access to your app's VM instances.

  • The geographical region of the VM instances used in the flexible environment is determined by the location that you specify for the App Engine application of your Cloud Platform project. Google's management services ensures that the VM instances are co-located for optimal performance.

Migrating from standard to the flexible environment

If you have an application in the standard environment, you might want to move some services to the flexible environment. For guidance, see the recommendations for Python, Java, Go, and PHP.

To migrate specific services, see the instructions for Python, Java, Go, and PHP.

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