How does Google App Engine data store scale with Polls

If I have a poll application on GAE being simultaneously upda开发者_如何学Goted across several continents, given the app has been replicated across Google infrastructure, would the data store keep accurate count? Do I need any design consideration for such application?

Applications aren't actually replicated across Google's infrastructure worldwide. If you're using the Master-Slave datastore (the default until very recently), everything you do is strongly consistent, and your reads are all served from a single datacenter (with data replicated to another datacenter as a backup, but not to serve requests ordinarily). With the HR datastore, you do get eventual consistency outside of transactions, but I believe all of the data is in North America and the latency isn't anywhere near what you might expect if the data was being stored on different continents (and, in any case, you can use transactions).