It can also quite easily be solved by using something like nginx's proxy_cache_background_update and/or proxy_cache_lock, depending on wether it's permissible t

It can also quite easily be solved by using something like nginx's proxy_cache_background_update and/or proxy_cache_lock, depending on wether it's permissible to send stale responses. Then you could have the cache serve stale content until it's updated, and/or only allow one upstream connection to refresh the cache. But yeah, unless you allow stale responses or refresh the cache periodically as you suggest, you would still have requests which takes 10 second to complete, but you would at least not crush the upstream service.