Microservice design with Kubernetes - API gateway, communication, service discovery and db issues
Is API gateway a microservice I built for my app that can automatically scale? Or is it already a built-in function of kubernetes?
Kubernetes does not have its own API-gateway service. It has an Ingress controller, which operates as a reverse proxy and exposes Kubernetes resources to the outside world. And Services, which load-balance traffic between Pods linked to them.
Also, Kubernetes provides an auto-scaling according to the resources consumed by Pods, memory usage or CPU utilization and some custom metrics. It is called Horizontal Pod Autoscaler, and you can read more about it here or in the official documentation.
Service Discovery: Is this a problem with kubernetes at all? Does kubernetes automatically figure out this for you?
Service Discovery is not a problem in Kubernetes, it has an entity called Services responsible for this. For more information, you can look through the link.
Your other questions refer more to the architecture of your application.