Web Hosting Talk : Web Hosting Main Forums : Cloud Hosting : Google App Engine Scalability

[peter fisk]

One of the recent uses of Google's App Engine was as the platform for President Obama's "Town Hall Meeting" held this past March. The White House used an open-source Google project called "Moderator" to record questions and count votes (Moderator is built on the App Engine).

Here are the stats:
"...64,000 people tuned in to the whitehouse.gov site during the event. More than 92,000 people submitted more than 100,000 questions. Citizens could vote and Mr. Obama would answer the most popular queries. More than 3.6 million votes were cast."

Most of the votes were cast in the final hours before the cutoff. At the peak, the system was handling 700 QPS (queries per second) according to Google's Vic Gundotra.

So, it looks like App Engine has no problems scaling to large transaction loads.

[cwcw]

App Engine should be fine for this sort of apps where visitors' stickiness is not a concern, in terms of session handling. As front-end scaling goes, session replication is one of the tricky areas and I'm not sure if App Engine had solved that problem in a nice and simple way.

[peter fisk]

By "stickiness", I assume that you are referring to something like PHP's "_SESSION" variable.

App Engine prefers developers to use a REST (Representational State Transfer) architectural style where the server is assumed to be stateless:

"Stateless: each request from client to server must contain all the information necessary to understand the request, and cannot take advantage of any stored context on the server"

However, maintaining server state is possible. Here is a link to a web framework running on App Engine that enables server-side continuations:

http://helma-ng.appspot.com/