Some performance facts
Monday, February 08, 2010
2:20 PM
Some performance facts about AppEngine
Reads and writes to the datastore are handled differently
Writes never block; the datastore does the write while the application is running. 
Reads block until data is consistent. 
Thus "writing one datum" takes negligible time, while "writing and reading one datum" in sequence takes (potentially) longer than "reading one datum" later, after data is known to be consistent!