Even though I’ve talked about this in the past, I feel like it’s so important that it needs to be said again and memorized (in fact, get sticky notes and prepare to tag this to your walls). If you’re using public APIs, rely on the functionality they give you, but always have a backup plan.

Think about it, almost 50% of the current web applications rely on public APIs, put out there by Google, or Yahoo!, Amazon, or even one of the smaller players. The problem is when the APIs fail, when the terms and conditions for usage change and a big chunk of your application’s functionality is lost overnight, no questions asked and no warnings issued. What do you do then? If you have no backup plan to save the functionality provided by your API, you’ll have downtime and risk failure altogether.

So, when planning your web-application, keep in mind that the more in control of functionality you are, the less likely it is for it to fail. There is no set solution for substituting functionality provided by public APIs like, for example, Google Maps. And there’s no guarantee that anything will ever fail. But if you’re building a business, you better be ready for everything - good or bad.

Further reading:

Service dependency on the new web, Published October 27
Public APIs - Arghh, Published January 11th on Forest and the Trees
Web 2.0 and the Drive-by upgrade, Published October 24 on O’Reilly Weblogs