# Discard late replies with process aliases

Send hand-rolled request replies to a process alias, then deactivate the alias when the caller stops waiting.

```elixir
defmodule ReplyClient do
  def request(server, message, timeout) do
    reply_to = Process.alias()
    send(server, {:request, reply_to, message})

    receive do
      {^reply_to, value} ->
        Process.unalias(reply_to)
        {:ok, value}
    after
      timeout ->
        Process.unalias(reply_to)
        {:error, :timeout}
    end
  end
end
```

An alias is a reference that can receive messages on behalf of the process that created it. The server replies with `send(reply_to, {reply_to, result})`, not by sending to the caller PID.

Once `Process.unalias/1` deactivates that alias, later sends to it are dropped. A slow reply therefore cannot arrive in the caller's mailbox after the timeout and get mistaken for a future message.

Deactivating an alias does not cancel the server's work. If the operation itself must stop, add an explicit cancellation protocol or run it in a process you can terminate safely.

Current `GenServer.call/3` already uses aliases internally. Reach for `Process.alias/0` when implementing your own request/reply protocol around plain processes, ports, or custom messaging.

[Process.alias/0 docs](https://hexdocs.pm/elixir/Process.html#alias/0)


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Created by: almirsarajcic
Date: September 03, 2026
URL: https://elixirdrops.net/d/yhZsXAMa