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Re:Ask HN: How can ChatGPT serve 700M users when I can't run... by brookst on Saturday August 09, 2025 @01:01AM (#44844139)
But that’s not accurate. There are all sorts of tricks around KV cache where different users will have the same first X bytes because they share system prompts, caching entire inputs / outputs when the context and user data is identical, and more.

Not sure if you were just joking or really believe that, but for other peoples’ sake, it’s wildly wrong.

Re:Ask HN: How can ChatGPT serve 700M users when I can't run... by kossTKR on Sunday August 10, 2025 @11:59AM (#44856078)
Really? So the system recognises someone asked the same question and serves the same answer? And who on earth shares the exact same context?

I mean i get the idea but sounds so incredibly rare it would mean absolutely nothing optimisation wise.

Re:Ask HN: How can ChatGPT serve 700M users when I can't run... by fc417fc802 on Sunday August 10, 2025 @05:34PM (#44858498)
Even if that were the case you wouldn't be wrong. Adding caching and deduplication (and clever routing and sharding, and ...) on top of timesharing doesn't somehow make it not timesharing anymore. The core observation about the raw numbers still applies.
Re:Ask HN: How can ChatGPT serve 700M users when I can't run... by brookst on Monday August 11, 2025 @04:50PM (#44869322)
Yes. It is not incredibly rare, it's incredibly common. A huge percentage of queries to retail LLMs are things like "hello" and "what can you do", with static system prompts that make the total context identical.

It's worth maybe a 3% reduction in GPU usage. So call it a half billion dollars a year or so, for a medium to large service.

Re:Ask HN: How can ChatGPT serve 700M users when I can't run... by throwaway2037 on Thursday August 14, 2025 @02:19AM (#44897276)

    > It's worth maybe a 3% reduction in GPU usage. So call it a half billion dollars a year or so, for a medium to large service.
So if 3% is 500M, then annual spend is ~16.6B. That is medium sized these days?