Bleeding out the akka-ness is a feature, at least if you live in akkaland. For example:

    path("get_a_list" / PathElement) { externalKey =>
      get {
        complete {
          for {
            internalKey <- redis.get("internal_keys_from_external":externalKey)
            finalResult <- redis.smembers(internalKey)
          } yield (finalResult.toList)
        }
      }
    }

Spray already expects an akka future, as does everything else, so this library fits in perfectly.