Imagine you’re launching a new online store. Decades ago, you’d have to buy a rack of servers, hire someone to set them up, and worry about cooling and power. Today, you can open a web browser and within minutes have a virtual server running in a data centre hundreds of miles away, paying only for what you use. That’s the promise of cloud computing — and behind the scenes, service-oriented architecture (SOA) makes it agile and reusable.