Once you start to build your microservice application via Docker, you'll need to have a Docker registry to put your container image in. Docker hub offers you free public repositories, however, in some cases you might want to make your image private due to business needs or organization policy.
Docker hub offers the private repository, which only allows authenticated users to push and pull your images, and is not visible to other users. However, there is only one quota (repository) for a free plan. You may pay to increase the number of private repositories, but if you adopt the microservices architecture, you will need a large number of private repositories:
Docker hub with a paid plan is the easiest way to set up your private registry, but there are some other ways to set up your own private Docker registry, which the unlimited Docker image quota locates inside your network. In addition, you can also use other cloud-provided registry services to manage your private registry.