Mollom is one of those cool SaaS companies every developer dreams of creating when they wrack their brains looking for a viable software-as-a-service startup," writes Todd Hoff. Mollom is a spam killing SaaS that competes with services like Akismet and Recaptcha by combining both machine learning and captchas (we've covered before here when the company was a ReadWriteWeb sponsor)."
Mollom runs on just two geographically distributed servers, both running a Java application server and Cassandra. And those two servers handle 100 API calls a second for companies like Warner Brothers, Fox News and The Economist. Hoff was so impressed by the service, and the fact that it runs on only two servers, that he decided to interview the developers behind the project.
Mollom can run on such minimal infrastructure because its machine learning algorithms and its architecture are so efficient. Hoff goes into far more detail on his site, but here's one interesting tactic: it uses client-side load balancing:
- Management of the client list is through an API. Each client has a list of available servers it can use.
- Each client can get a different list of servers to use. Paying customers can be provided a list of closer servers to reduce latency.
- When a server fails the clients will try the next server in the list.