> Looking at things more closely, the only thing that you're truly locked into with GAE is the esoteric nature of the datastore. This isn't any worse than picking say MySQL vs. Oracle or Riak vs. Mongo.
Sure it is. If you pick the wrong DB your only locked into that DB. You pick GAE and you're locked into GAE's DB.... and GAE. I can move my MySql db to another cloud provider.
@latchkey I think you are missing the point the MatthewPhillips is making. With GAE's DB there is nowhere to move, so if you want to move you would have to migrate your data to a different DB engine. If your hosting/cloud provider uses something standard like MySQL you can find another provider or roll your own if you decide to migrate out.
Your analogy of moving to another cloud provider is incorrect. Unless you've been 100% database agnostic, you can't just migrate your schema and data from say MySQL to Postgres.
With the datastore on GAE, you can get your data out of it and move it into something like MongoDB. I'd argue that it would probably be less code to move to MongoDB because the datastore has all sorts of esoteric issues that you have to code around (like the way that entity groups and transactions are handled).
In terms of the rest of your application, it is just a standard webapp in whatever platform you choose. The .war file I have for GAE will run just fine in Tomcat. The only real lockin is the way you store your data.
Sure it is. If you pick the wrong DB your only locked into that DB. You pick GAE and you're locked into GAE's DB.... and GAE. I can move my MySql db to another cloud provider.