Django app freezing with a few concurrent requests

I have a django app without views, I only use it to provide a REST API using django-piston package.

Since I have deployed it to amazon-ec2 with mod-wsgi, after some requests it freezes, and the CPU goes to 100% of usage divided by python and httpd processes.

I'm using Postgres 8.4, Python 2.5 and Django 'ENGINE': 'django.contrib.gis.db.backends.postgis开发者_JAVA技巧'.

Logs don't show me any problem. How can I debug the problem?

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Sounds like you're in a micro instance. Micro instances are able to burst large amounts of cpu for a VERY short amount of time, after that they must drop to very low background levels for an extended duration or else amazon with harshly throttle it. If you're getting concurrent requests most likely even a lightly cpu intensive app would cause the throttling to kick in.

Micro instances are only usable for very very light traffic on something like a very basic blog and that's like it.

Their user guide goes into this in detail: Micro Instance guide.