Microsoft Azure is Microsoft's cloud computing platform, launched in 2010 as a direct competitor to Amazon Web Services and the second-largest cloud provider by global revenue. Azure's strategic advantage is its integration with Microsoft's enterprise software ecosystem — Windows Server, Office 365, Active Directory, and the .NET development stack — which made it the natural choice for organizations already committed to Microsoft infrastructure. The platform offers a full spectrum of services from Infrastructure as a Service (virtual machines, storage, networking) to Platform as a Service (managed runtimes, databases) to Software as a Service (Office 365, Dynamics). Azure's systems significance is as a case study in ecosystem lock-in: the cloud platform that succeeds not by being the best but by being the inevitable choice for customers already trapped in a software ecosystem. The question Azure poses is whether cloud computing is a market or a moat.