SuccessFactors runs on a standard three tier model – web servers, app servers and database servers. The company predominantly uses blade servers, an unnamed hypervisor and spinning disk for storage. "The stack is built such that we can expand horizontally, we can add more web servers, more database servers, more app servers, more disk if required," Harmer said. "And if our data centre provider can’t extend the cage, we can put it within another area of the data centre."