What are the rules of thumb when trying to decide if developing on Google App Engine platform is worthwhile

I have an idea for a web application and I am currently researching different platforms. I am really interested in Google App Engine, but it looks like it works pretty good for certain application types while it is less suitable for others (there are horror as well a开发者_JAVA技巧s success stories e.g. Goodbye Google App Engine vs. Why we are really happy with Google App Engine

There is also a similar negative story in this thread from 1 year ago, concluding GAE was not ready for commercial production platform: GAE as Production Platform. There are also other threads from 2009 talking about data select limits (1000 rows) that has since been lifted.

My app will essentially perform some mathematical analysis based on data pulled from external data feeds (could be some substantial amount of data), it would be real time only the first time data is downloaded for a specific item at hand and then stored and retrieved locally from the database at that point. There will be some additional external data pulls as scheduled intervals.

Based on this brief description, should I even bother starting on GAE? In general, what are the rules of thumb to try and decide if developing on GAE is suitable for a problem at hand? Also, what are the good examples of Apps in Production that use GAE. It looks like GAE App Gallery is not around anymore, but I would definitely appreciate any Web 2.0 App examples running on the app engine.

In your specific case I would double check these factors:

a. Is the mathematical analysis a long running CPU intensive job?

GAE is not designed for long running CPU intensive computational Jobs; this would lead to have an high billing cost and would force you to design your application to avoid some GAE limitations (10 minutes max per job, limited soft memory, CPU quota, etc. etc.).

b. Are you planning to retrieve external data using a mainstream API (twitter, yahoo, facebook)?

Your application shares the same pool of IPs with other applications; if the API you want to adopt does not allow authenticated request, your application will suffer hiccups caused by throttling/quota limits errors. I faced this problem here.

App Engine should work fine for your application. It's generally designed to serve, and to scale, sites that serve mostly user-facing traffic. Applications that it's not suitable for are things such as video transcoding, which rely heavily on backend processing, or things that have to shell out to native code, such as 3D graphics, etcetera.

Depends on what type of mathematical analysis are you doing. If your application is heavy in I/O, I would give it some pause. On GAE, you're kind of limited in your I/O options. You basically have the following:

• RAM: I can't recall exactly, but GAE imposes a hard limit of around 200MB of RAM.
• Datastore: You get plenty of space here, but it's slow compared to a cached local file system.
• Memcache: Faster than datastore, but not nearly as fast as a cached disk. And worse, it's a cache, so there's no guarantee that it won't get wiped out.
• External sources: These include calling out to external web-pages. Lots of flexibility, but very slow.

In sum, I would perhaps look at other options if you're doing heavy I/O on a medium-size dataset (>20MB and ~<2GB). These are probably non-issues for 90% of web-apps, although you should be aware of them.

All the negatives aside, working on GAE is a joyous experience. You spend more time programming and less time configuring. And it's really cheap.