A solid understanding of fs2 and http4s is essential for a more comprehensive grasp of Scala. If you are looking for an efficient and speedy polymorphic stream processing library, then FS2, or Functional Streams for Scala, is for you. It is compatible with Cats-effect typeclasses and can be used with other effect libraries. Built on FS2, HTTP4S is the ideal companion topic for this course and is the minimal Scala interface for your HTTP services.