The App Engine standard environment has two generations of runtime environments. The second-generation runtimes significantly improve the capabilities of App Engine and remove some of the limitations of the first-generation runtimes. This page describes the similarities and differences between the first- and second-generation runtimes.
| Second-generation | First-generation | |
|---|---|---|
| Supported languages |
Python 3 Java 11 Node.js PHP 7 Ruby Go 1.12+ |
Python 2.7 Java 8 PHP 5.5 Go 1.11 |
| Language extension and system library support | Any extension or library | Python 2.7, PHP 5.5: Allowlisted extensions and libraries Java 8, Go 1.11: Any extension or library |
| Supported APIs |
To access full-featured Google Cloud services, use the open source Cloud Client Libraries. When updating to the Python 3, Java 11, or Go 1.12+ runtimes, you can continue using many of the App Engine bundled services. To learn more, see the Python 3, Java 11 and Go 1.12+ guides for details. |
Proprietary App Engine APIs |
| For data persistence, use Datastore
(Python developers can also use
Cloud NDB),
Firestore (requires new project),
or Cloud SQL. |
App Engine Datastore API | |
| For image processing,
Imgix
is recommended.
Otherwise, use Rethumb if you prefer having a free tier. |
App Engine Images API | |
| For messaging, use a third-party mail provider such as SendGrid, Mailgun, or Mailjet. | App Engine Mail API | |
| For caching app data, create a Memorystore instance and connect it to your app using Serverless VPC Access. | App Engine Memcache API | |
| For searchable document indexes, host any full-text search database such as ElasticSearch on Compute Engine and access it from your service. | App Engine Search API | |
| For push queues, use
Cloud Tasks. For pull queues, use Pub/Sub. |
App Engine Task Queue API | |
| For user authentication, use any HTTP-based authentication system, such as OAuth 2.0, or Firebase Authentication. | App Engine Users API | |
| External network access | Full access | Python 2.7, PHP 5.5: Via URL Fetch API Java 8, Go 1.11: Full access. |
| File system access | Read/write access to /tmp |
Python 2.7, PHP 5.5: None Java 8, Go 1.11: Read/write access to /tmp |
| Language runtime | Unmodified, open source runtime | Modified for App Engine |
| Isolation mechanism | gVisor-based container sandbox | Proprietary |
App Engine first-generation runtime support
There are no plans to deprecate additional App Engine first-generation runtimes at this time. The second-generation runtimes represent the future direction of App Engine; however, developers and customers using the first-generation runtimes will continue to receive support and required system updates.
To learn more about the support plan for first-generation runtimes, see Long-term support for legacy runtimes.
Similarities between first- and second-generation runtimes
- Nearly instantaneous scale-up time to respond to traffic spikes
- Applications are built using the same build process
- Same SLA for GA services
- Identical
gcloudcommand support and the same GCP console interface - Free tier
First- to second-generation runtime migration resources
Migration guides are available for each language runtime on the Long-term support page.