When its App Engine goes out of preview Google is changing the way it charges for its computing power and this is going to push some developers out of Google's cloud and with nowhere to go.

Google's new pricing model does away with billing by CPU time, and now charges by on-demand frontend/backend instances.

The cost of an instance isn't unreasonable at $0.8 per hour but this is charged even if the instance is doing nothing and this makes a big difference. On the old pricing model an instance that was sitting idle cost next to nothing but now it will cost something to do nothing. Users (see Hacker News) recalculating their future charges are discovering that they can look forward to some very steep price hikes - $500/month to $3000/month for example.

To try to sugar this unpalatable news the announcement is headlined with the good news: $50 Credit for new billing signups and budget changes; to help allay developers' dismay, Google is extending a one-time credit of $50 to both those whose apps were previously free or paid as long as they sign up or make necessary changes prior tp October 31, 2011.

Again in an attempt at positive spin, the announcement also mentions an article to help you optimize your application.

Of course it is always the customer's right to move to another supplier if they don't like the price on offer. However in the case of Google App Engine there is no easy move. App Engine is very Google-specific and to move to another virtual machine setup is going to be a big migration task.

Given that Google has had a lot of time to think about its pricing structure and developers have had as much time to get deeply committed to the platform it seems even more unfair.

The lesson to be learned is the old one of "don't pick a technology that only has a single supplier". Software may be easier to recast than hardware but porting to a new platform is still an expensive task. Perhaps it points up the problems with the whole "cloud" enterprise as currently, without standards, moving even from the most open of infrastructure is going to be painful. Compared to traditional hosting, cloud infrastructure may be novel but it is also a trap waiting to be sprung.

There is also a lesson to be learned about not getting too deep into a beta system that hasn't made clear its future pricing.

At present it seems that either Google rethinks its pricing structure (unlikely) or a lot of Google App Engine apps are about to disappear.

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