Application portability

Services written for the App Engine flexible environment tend to be more portable than services designed to run in the standard environment. This is largely due to design considerations developers must make to get the most out of the standard environment.

Nowhere is this more clear than in the case of custom runtimes, where basically any service packaged into a Docker image can be made to run in the flexible environment.

The generally prescribed approach for service integrations in the flexible environment is to use the Google Cloud Client Libraries, which function independently from App Engine. This largely reduces coupling with the App Engine platform. Service using these client libraries can effectively operate anywhere with little modification. For example, a service written for the flexible environment can be ported to other services such as Compute Engine, Kubernetes Engine, other public cloud services, or on premises with relative ease. As container technologies continue to gain mainstream support, services written for the flexible environment will increase in portability.