[happy_dino]

  // Some example methods which might spend waiting for other
  // services (calling the database, sending emails).

  def getEMailForUsername(username: String) =
    future { DB.Users.find(_.name == username).get.email }

  def sendPassordRecoveryMail(email: EMail, message: String) =
    future { SMTPService.send(email, message) }

  // Future/Promises API:
  def resetPassword(username: String) =
    for {
      email <- getEMailForUsername(username)
      result <- sendPassordRecoveryMail(email, "some message")
    } yield result


  // Async API:
  def resetPassword(username: String) =
    async {
      val email = getEMailForUsername(username)
      val result = sendPassordRecoveryMail(email, "some message")
      await(result)
    }

@smegel: I don't see any “callback hell” or “code that does look like spaghetti” here. By the way, I'd love to see a link to “Scala's synchronous API” and that mystical “far less attractive callback based API”. Or are you making things up again?