Do I need an API gateway?

If you're using Istio, do you still need an API gateway? In the past, Istio has been primarily concerned with routing traffic for services. It got traffic into the cluster and figured out where to route it to. API gateways have more typically been focused on application-level functionality such as authentication, authorization, input validation, and logging.

For example, earlier in this chapter we identified schema input validation as a process that needs to be repeated for each call and shouldn't need to be done manually. This is important to protect against attacks that can leverage unexpected input and also makes for a better developer experience to provide feedback to developers sooner in the integration process. This is a common function for API gateways, but is not available in Istio.

Another example of a function that is not built into Istio, but is common for API gateways, is logging authentication and authorization decisions and...