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It was quite fun to see, right after Tim O’Reilly pondered the lock in strategy for App Engine, that Chris Anderson posted that he had ported the SDK to App Drop.

Now, there are some concerns here as the SDK itself isn’t built for performance, security, etc…. but this is a great start in a very short period of time, and it shows where people can take it.

Waxy has a good write up:

This proof-of-concept was built in only four days and can be deployed in virtually any Linux/Unix hosting environment, showing that moving applications off Google’s servers isn’t as hard as everyone thought.

How does it work? Behind the scenes, AppDrop is simply a remote installation of the App Engine SDK, with the user authentication and identification modified to use a local silo instead of Google Accounts. As a result, any application that works with the App Engine SDK should work flawlessly on AppDrop. For example, here’s Anderson’s Fug This application running on Google App Engine and the identical code running on EC2 at AppDrop.

Of course, this simple portability comes at the cost of scalability. The App Engine SDK doesn’t use BigTable for its datastore, instead relying on a simple flat file on a single server. This means issues with performance and no scalabity to speak of, but for apps with limited resource needs, something as simple as AppDrop would work fine.

Chris said: “It wouldn’t be hard for a competent hacker to add real database support. It wouldn’t be that hard to write a Python adapter to MySQL that would preserve the BigTable API. And while that wouldn’t be quite as scalable as BigTable, we’ve all seen that MySQL can take you pretty far. On top of that, you could add multiple application machines connecting to the central database, and load-balancing, and all that rigamarole.”

And for data, you can write built-in services that export your data from the store.