Absolutely not. You can use Cloud Datastore, or you can connect to any database that can communicate over sockets or http, including Cloud SQL. Of note is that Datastore has a free tier, Cloud SQL does not, and Socket usage can incur (some) cost when communicating with other databases.
I've seen many Python apps that connect to a free MongoDB instance hosted on Mongolab.
(also worth noting that Node.js support for App Engine is currently in beta.)
> also worth noting that Node.js support for App Engine is currently in beta.
Is this public? I have been waiting to hear this for ages! Great News.
I am planning a switch to node simply so I can run the same code on the front and back end. I was not looking forward to learning how to administer a server.
I've seen many Python apps that connect to a free MongoDB instance hosted on Mongolab.
(also worth noting that Node.js support for App Engine is currently in beta.)
(disclaimer: I work for Google on Cloud Platform)