Benchmarks for various Google App Engine Datastore operations?

A recent question regarding the datastore and how long a query should run got me thinking - has anyone compiled a nice set of benchmarks that would demonstrate what "typical" results should be for datastore performance? I know that every entity kind will have different performance characteristics, but it would be great to be able to see times for a few representative types of entities, so we know if we're doing something wrong (for e开发者_Python百科xample, if we see that our query is taking much longer than the benchmark, we might know to check for non lazily fetched relationships, or to verify that we are using the api properly to batch fetch things.)

I think that you can check on the system status page the "typical" latencies for some transactions, but due to the load balancing, on a real application, this time can vary a lot, depending on the application current load. Indexes, entity size, number of registers, etc would also affect the results. It's hard to make a comprehensive set of tests.

I think that the best way to have an idea of how an application will perform under load is to do a load test according to the tips of this article: code.google.com/appengine/articles/load_test.html