I have a django application and a mysql database table having around 30,000 entries. 
I have to process each entry one by one, do some computation and store the result   in database.
When I start processing, the time taken to process 100 entries is around 40 seconds. But this time keeps on growing. So after processing 1000 entries, the time goes to 1 minute, then after processing 2000 entries, the time to compute 100 entries move to 1 minute 30 seconds. 
If I stop the server, and start computing again from say 2000th entry, then the time taken to process 100 entries becomes 40 seconds again, but keeps on increasing as more entries are processed.
Does anyone know why is this happening?
Sounds like you need an index.
Don't process one row at a time; use SQL to process all rows 'simultaneously'.  Describe the processing; we may be able to get more specific.
Django queries gets slower over time