alt Hacker NewsI continue to be surprised that in these discussions correctness is treated as some optional highest possible level of quality, not the only reasonable state.
Suppose we're talking about multiplayer game networking, where the central store receives torrents of UDP packets and it is assumed that like half of them will never arrive. It doesn't make sense to view this as "we don't care about the player's actual position". We do. The system just has tolerances for how often the updates must be communicated successfully. Lost packets do not make the system incorrect.
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If you’re live streaming video, you can make sure every frame is a P-frame which brings your bandwidth costs to a minimum, but then a lost packet completely permanently disables the stream. Or you periodically refresh the stream with I-frames sent over a reliable channel so that lost packets corrupt the video going forward only momentarily.
Sure, if performance characteristics were the same, people would go for strong consistency. The reason many different consistency models are defined is that there’s different tradeoffs that are preferable to a given problem domain with specific business requirements.
Back in the day there were some P2P RTS games that just sent duplicates. Like each UDP packet would have a new game state and then 1 or more repetitions of previous ones. For lockstep P2P engines, the state that needs to be transferred tends towards just being the client's input, so it's tiny, just a handful of bytes. Makes more sense to just duplicate ahead of time vs ack/nack and resend.