A client middleware is something that you can add on to a Client to extend its functionality. Some examples of this would be: * Logging middleware that logs response status codes/headers/etc * Tracing middleware that wires in functionality for Open Tracing or similar * Authentication middleware that would automatically add an

Higher kinded types are types which take types which take types as parameters. I know, it burns the eyes just to read that sentence. So let's try to break it down. A type which takes a type is something we've already dealt with in a prior

Generic types in Scala allow for abstractions that cover different, potentially unrelated, types. A good example is the List type in Scala. If it weren't for generics, we'd have two main options for implementing lists: 1. Create a different List type for each type of elements

As a newcomer to functional programming, I thought mutability was prohibited. Although I figured out how to use immutability in most situations, I found there were obvious cases where it doesn’t work such as modeling and updating in-memory state (e.g. in-memory caches and counters). I was wrong to