As redtuesday correctly noticed, Akka HTTP is a successor of Spray.io. Mathias Doenitz, the main author of Spray.io, worked on Akka HTTP as well. They are simil

As redtuesday correctly noticed, Akka HTTP is a successor of Spray.io. Mathias Doenitz, the main author of Spray.io, worked on Akka HTTP as well. They are similar in many places, just powered by different "engines". Akka HTTP is built above new Akka Streams, while Spray.io is powered by plain Akka. But, for example, routing DLS is very similar. Our main API is in Spray, but when I tried Akka HTTP for a new microservice, I actually reused most of things from our customised stuff above Spray.