The migration guide can be found
in our documentation. The main difference is that instances are now
Compute Engine VMs, which means the
old App Engine API is no longer accessible (since it only works from the App Engine Standard environment). Migrating to Flex simply means migrating your code to using the new
Google Cloud Client Libraries.
All of your Datastore data will still be accessible if you deploy a Flexible version of your code to the same project. But you will need to use the new
Objectify version 6 which uses the new Client Libraries by following their
code migration guide.
The
Firebase Libraries are also not App Engine specific (meaning they are accessible from outside of App Engine) and can be used from anywhere (e.g Flex,
Standard, etc). For a quick example on how to use Firebase from the App Engine Flexible environment you can view their
quickstart tutorial.
- Note that Google Groups if for general product discussions and not for technical support. For any further technical support in migrating your code it is recommended to post
your detailed questions to
Stack Overflow using the supported cloud tags.