There have been a number of posts attacking App Engine recently, and a lot of good discussions have come out of them. The two things issues that seem to get brought up most are app design and reliability.
- Reliability: App Engine reliability used to be horrible, but it's getting better.
GAE was the first service I ever developed for where reliability was an issue. I've hosted apps on Linode, Slicehost, EC2, and my experience with those companies caused me to dismiss claims of downtime and the importance of an SLA.
Nothing sucks more then seeing your system go down for days at a time, and not being able to do anything about it. I'm glad that GAE is addressing this issue, but I'd be wary of running anything commercial on their services without buying a business plan.
- App Design: Pretty much everyone agrees that you have to write applications the way GAE wants you to, or you'll fail.
The built in GAE Python library is great for writing simple, highly scalable websites, but it's too limited to develop complex applications on. Our application has over 20KLOC and uses numerous third party libraries. In practice, we found that it was difficult and time-consuming to write our application without turning to a more established framework like Django. We were also concerned with the vendor lock-in that would be caused by building on library that could only be run on GAE. Projects like TyphoonAE (http://code.google.com/p/typhoonae/) are starting to make this less of an issue, but they aren't mature enough to provide an exit strategy.
We built our application on appenginepatch, a third party port of Django to GAE. Django was not designed to run on a non-relational DB, and GAE was not designed to handle a heavy framework like Django. Our decision to build things our application on Django ultimately lead to most of our problems, but eventually saved our skin when we decided to switch away from GAE.
Well, my motivation in writing the blog was in response to the people who replied to the last HN story on App Engine saying the author was clueless and just didn't know what he was doing. For what it's worth, there are a lot of other very bright people that have had the same issues and came to the same conclusion.
I think it's just that developing for GAE is just so different from developing on a typical LAMP stack that there inevitably a fairly steep learning curve. That combined with the (well documented) limitations you just have to find new ways of solving problems. The fact that this author thinks that other article was a "good read" doesn't inspire a lot of confidence in what this guy has to say.
I don't know if developing on the App Engine is still as bad as it was before. Maybe it's changed in the last few months that we've been on EC2
From what I've heard, things have dramatically improved from how they were a few months ago.
It's not a new trend. App Engine has had issues for a long time. Here's an article I wrote early last year about some of its problems and proposed solutions that the GAE team could use to fix them:
But, despite the various problems, I still use App Engine for various applications. There are few platforms that can even compare to its power and simplicity. And good luck finding a NoSQL datastore which offers the power and scalability of App Engine's one.
In fact, if there was a decent open source alternative to the datastore, I'd switch away almost immediately.
