Runtime lifecycle

The App Engine flexible environment runtimes use open source components that are maintained by their respective communities. The runtimes are identified by their language version, for example, Java 17, Python 3.10, and so forth.

Diagram outlining the stages in the lifecycle of an App Engine runtime

Google provides support for a runtime during General availability (GA). During this support window:

  • Runtime components are regularly updated with security and bug fixes.
  • To maintain stability, App Engine avoids implementing breaking features or changes into the runtime. Breaking changes will be announced in advance on the runtime-specific release notes.

When a language version is no longer actively maintained by the respective community, App Engine will also stop providing maintenance and support for that language runtime. Before a runtime reaches the end of support phase as described in the runtimes support schedule, Google will provide a notification to customers.

Google may make changes to any runtime's support schedule or lifecycle in accordance with the terms of your agreement for the use of Google Cloud platform services.

Custom runtimes

Custom runtimes allow you to define new runtime environments which may include additional components like language interpreters or application servers.

Custom runtimes are not impacted by the runtime lifecycle policy.

Runtime lifecycle

GA-level support End of Support Deprecated Decommissioned
Creation & redeployment Yes No No No
Project Configuration Updates Yes Yes No No
Running existing workloads Yes Yes Yes No
UI & CLI Warnings Yes Yes No No
Language patches Automatic No automatic updates No automatic updates No automatic updates
Patching APIs & SDKs Automatic No automatic updates No automatic updates No automatic updates
Customer Support GA-level support No runtime support No runtime support No runtime support

Notification period

App Engine will begin issuing in-app notifications 90 days before the application reaches end of support. Upon notification, you should prepare to upgrade your application to a newer runtime that is supported in the flexible environment .

End of support

When runtime components reach the end of support date:

  • Google will no longer apply security updates or patches to components of the runtime environment.
  • Your application will continue to run and receive traffic.
  • You will no longer be able to create and/or update the application on the unsupported runtime.
  • Issues arising from the use of an unsupported runtime will not be eligible for technical support

We strongly encourage you to upgrade your application to a supported runtime version as soon as it becomes available to continue receiving security updates and being eligible for technical support.

Alternatively, you can redeploy your application using a custom runtime.


If Google allowed your Organization to re-enable deployments in an unsupported runtime, Google will remove that ability once the runtime is deprecated.

Where practicable, we will make reasonable efforts to notify you in advance of the deprecation by in-app notifications or other means. In certain instances, including in circumstances involving critical security vulnerabilities or similar high severity issues, advance notice may not be practicable.


Applications that continue to use a decommissioned runtime may be disabled without further notice. You must choose a more up-to-date runtime to deploy your application.

See the runtimes support schedule for key dates.