Another very important support function is an edge server. As we already described in Chapter 1, Introduction to Microservices, in the Edge server section, it can be used to secure a microservice landscape, which involves hiding private services from external usage and protecting public services when they're used by external clients.

Initially, Spring Cloud used Netflix Zuul v1 as its edge server. Since the Spring Cloud Greenwich release, it's recommended to use Spring Cloud Gateway instead. Spring Cloud Gateway comes with similar support for critical features, such as URL path-based routing and the protection of endpoints via the use of OAuth 2.0 and OpenID Connect (OIDC).

One important difference between Netflix Zuul v1 and Spring Cloud Gateway is that Spring Cloud Gateway is based on non-blocking APIs that use Spring 5, Project Reactor, and Spring Boot 2, while Netflix Zuul v1 is based on blocking APIs. This means that Spring Cloud Gateway should be able to handle larger numbers of concurrent requests than Netflix Zuul v1, which is important for an edge server that all external traffic goes through.