> How does one ensure cache consistency on all edges?

I wouldn't - you can never really rely on anything being consistent cached, there will always be stuff that doesn't follow the standards and thus can give an inconsistent state for one or more users.

What I'd do, would simply to be to purge the files whenever needed (and possibly warm them up if you want them to be "hot" when visitors arrive), sure the first 1-2 visitors in each location might have a bit slower request, but that's about it.

Alternatively you could just put a super low cache-control, when you're using proxy_cache_background_update and proxy_cache_use_stale_updating, nginx will ask the origin server if the file has changed - so if it haven't you'll simply get a 304 from the origin (if the origin supports it) - so you'll do more requests to the origin, but traffic will be minimal because it just returns 304 not modified (plus some more headers).

Best Regards,
Lucas Rolff


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