It's worth thinking a bit about the long-term plan when your hairdresser chats away about a brilliant Web application while cutting your hair. Some whispers I've heard suggest that Google might just steal your application, perhaps copying it. I'm not sure why hosting it with Google would make it any easier for them, but maybe forcing you to map it onto their architecture might help a bit.

The Bottom Line Google App Engine preview release Google, google.com/appengine Preview   Cost: The beta program is free but closed to new members. Applications are limited to daily quotas such as 2,000 e-mail messages, 200 million CPU megacycles, and 2.5 million data store calls. The documentation suggests that users will be able to spend money to expand the quotas. Platforms: Any Python 2.5 Web application that operates in a sandbox that excludes actions such as writing to the file system. Google has integrated several standard Web frameworks to simplify the development process. Bottom Line: Google App Engine hides the grime of deploying a scalable application to a number of servers. The limitations on the sandbox make this "cloud" best for dynamic Web sites that act as a relatively thin layer of business logic sitting on top of a data store. Google's Python/Django framework makes developing simple applications quick, and the database structure encourages scalable design by excluding joins. On the downside, there's not much support for AJAX, porting some applications will require rethinking the database schema, and your coders better like Python, which is currently the only option. About our Reviews and Scoring Methodology

There are any number of competitors. Amazon has its own cloud, but it takes a very different approach, giving the user an empty Linux shell. That may offer plenty of freedom, but it offers none of the handholding. It will probably take you longer to install a JVM on Amazon's Elastic Compute Cloud than to spin up a three-page Web site with Google's App Engine. But Amazon's SimpleDB also offers a richer API, including real Web services for REST and SOAP queries.

The biggest competitors may be the old-school Web hosting programs that let you share a server for a few bucks a month. They may not scale automatically, but they give you plenty of control and an older, more established type of user agreement. And while they may not be as magic as Amazon, they have a number of tools for migrating customers to bigger boxes. The last time I asked my shared hosting service to move to a new server with a different version of MySQL, it was done in an hour or two. That's not automatic, but it only took an e-mail message.

Work in progress
It is almost unfair to review the Google App Engine when it is just a beta operation, but Google has a habit of leaving some tools in beta form for a long time. There are a number of places where the documentation and the code suggest that Google will add more functionality pretty soon. The basic framework and the database are both quite nice, although limited. I can imagine Google adding better automatic features for generating the CRUD (Create, Update, Delete) routines common in these applications. Integration with Google's Wallet might also be quite useful, although it's bound to be complicated by the banking system. Some people have already experimented with mapping the Google Web Toolkit to the system, even though that's written in Java and translated into JavaScript.

Google might also provide some good tools that allow the different hosted applications to share user information, essentially allowing a user to move their preferences and some of their data to other applications. This kind of inter-application linking could be pretty cool.

Time will tell what Google delivers. In the meantime, this is a good sandbox for playing with simple database applications. There's a very good reason why the beta version has a waiting list.

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