This chapter provides an overview of cloud computing and microservices. Resource sharing has been the driving force behind the evolution of computing. The computing paradigm has experienced an evolution from stand-alone computing to cluster computing, and then from cluster computing to cloud computing. In stand-alone computing, sharing means that multiple processes execute concurrently in a computer. Cluster computing extends sharing across computer boundaries. Cloud computing enables server programs to run successfully anywhere on the cloud. Cloud computing has promoted informationization, bringing about new challenges to servers. Servers are facing the double pressure of increasing data volume and customer requests. For servers, the strategies and methods to achieve efficiency, resilience, scalability, availability, security, and consistency, as well as rapid development and deployment, rapid revision and upgrade, and fast startup, are collectively known as microservice technologies.