Feedback on using Google App Engine?

I am using GAE to host several high-traffic applications. Like on the order of 50-100 req/sec. It is great, I can't recommend it enough.

My previous experience with web development was with Ruby (Rails/Merb). Learning Python was easy. I didn't mess with Django or Pylons or any other framework, just started from the GAE examples and built what I needed out of the basic webapp libraries that are provided.

If you're used to the flexibility of SQL the datastore can take some getting used to. Nothing too traumatic! The biggest adjustment is moving away from JOINs. You have to shed the idea that normalizing is crucial.

Ben

I have tried app engine for my small quake watch application http://quakewatch.appspot.com/

My purpose was to see the capabilities of app engine, so here are the main points:

1. it doesn't come by default with Django, it has its own web framework which is pythonic has URL dispatcher like Django and it uses Django templates So if you have Django exp. you will find it easy to use
   • But you can use any pure python framework and Django can be easily added see http://code.google.com/appengine/articles/django.html google-app-engine-django (http://code.google.com/p/google-app-engine-django/) project is excellent and works almost like working on a Django project
2. You can not execute any long running process on server, what you do is reply to request and which should be quick otherwise appengine will kill it So if your app needs lots of backend processing appengine is not the best way otherwise you will have to do processing on a server of your own
3. My quakewatch app has a subscription feature, it means I had to email latest quakes as they happend, but I can not run a background process in app engine to monitor new quakes solution here is to use a third part service like pingablity.com which can connect to one of your page and which executes the subscription emailer but here also you will have to take care that you don't spend much time here or break task into several pieces
4. It provides Django like modeling capabilities but backend is totally different but for a new project it should not matter.

But overall I think it is excellent for creating apps which do not need lot of background processing.

Edit: Now task queues can be used for running batch processing or scheduled tasks

Edit: after working/creating a real application on GAE for a year, now my opnion is that unless you are making a application which needs to scale to million and million of users, don't use GAE. Maintaining and doing trivial tasks in GAE is a headache due to distributed nature, to avoid deadline exceeded errors, count entities or do complex queries requires complex code, so small complex application should stick to LAMP.

Edit: Models should be specially designed considering all the transactions you wish to have in future, because entities only in same entity group can be used in a transaction and it makes the process of updating two different groups a nightmare e.g. transfer money from user1 to user2 in transaction is impossible unless they are in same entity group, but making them same entity group may not be best for frequent update purposes.... read this http://blog.notdot.net/2009/9/Distributed-Transactions-on-App-Engine