If they required of you to implement once-and-only-once reliable delivery of messages over a network, then I would argue they don't really understand the proble

If they required of you to implement once-and-only-once reliable delivery of messages over a network, then I would argue they don't really understand the problem themselves. This blog post does a pretty good job of describing the problem: http://bravenewgeek.com/you-cannot-have-exactly-once-delivery/ http://bravenewgeek.com/you-cannot-have-exactly-once-deliver... I would not feel bad about missing this question. Distributed systems are hard!