It was the combination of EC2 and S3 - storage and compute, two primitives linked together - that transformed both AWS and the technology world. Startups no longer needed to spend their venture capital on buying servers and hiring specialized engineers to run them. Infrastructure costs were variable instead of fixed, and they could grow in direct proportion to revenues. It freed companies to experiment, to change their business models with a minimum of pain, and to keep up with the rapidly growing audiences of erupting social networks like Facebook and Twitter.
