Can any one explain how to Understanding Datastore Read Costs in App Engine?

Question

I am doing geoquery among 300 user entities with a result range 10.
I've maked a query for 120 times. For each query I got 10 user entity objects.
After this my app engine read operations reached 52% (26000 operations).
My user entity has 12 single value properties and 3 multi-value properties(List type).
User entity have 2 indexes for single value properties and 2 indexes on list type properties.
Can any one please help me to understand how google's appengine counts the datastore read operations?

Answer 1

As a start, use appstats. It'll show you where your costs are coming from in your app:

https://developers.google.com/appengine/docs/java/tools/appstats

To keep your application fast, you need to know:

Is your application making unnecessay RPC calls? Should it cache data instead of making repeated RPC calls to get the same data? Will your application perform better if multiple requests are executed in parallel rather than serially? The Appstats library helps you answer these questions and verify that your application is using RPC calls in the most efficient way by allowing you to profile your RPC calls. Appstats allows you to trace all RPC calls for a given request and reports on the time and cost of each call.

Once you understand where your costs are coming from you can optimise.

If you just want to know what the prices are, they are here:

https://developers.google.com/appengine/docs/billing

Answer 2

You can analyse what is going on under the hood with appstats: https://developers.google.com/appengine/docs/java/tools/appstats