Thread

1. jrochkind1 · 1790210927 · focus · HN ↗

   I had not actually realized what a mess Vary is.

   Wow, sometimes I think it's amazing the web works at all!

   1. saltcured · 1790211418 · focus · HN ↗

      It pains me to think about the important ones like varying on session cookie and authorization headers, and how badly some middleware can confuse things.

      We generate custom content for a given authentication context. We definitely want caching at the user agent, but we want the cache keyed by the authenticated identity. Otherwise something like logging out and logging in as a different identity can produce monstrously confused results when an SPA or similar mixes some cached and some fresh responses into one page.

      1. rmunn · 1790214657 · focus · HN ↗

         Cache invalidation, one of the two hard problems in computer science.

         I'm sure most people here already knows the joke, but for the lucky 10,000, here's the full joke:

         There are only two hard problems in computer science. Naming things, cache invalidation, and off-by-one errors.

         1. [deleted] · 1790216636 · focus · HN ↗

            [deleted]

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