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Not sure if this belongs here, but had the thought while trying the hit Stack Overflow during routine maintenance.

Does me hitting stackoverflow.com when its down cause issues on the servers? If so, how are they handled by the servers? Would sysadmins need to take any action?

If not, why? How are requests handled when the server is down?

I appreciate that this is a problem probably solved in the 90s, but I can't think of an appropriate google search for this question, and this seemed far more relevant a place for it than Stack Overflow. My gut feeling would be that a separate server handles the traffic.

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Not sure about stackexchange specifically. But for most large sites you probably aren’t directly connecting to servers providing a service. Instead you are hitting a load balancer or proxy of some sort. During an outage or planned work the proxy would send your requests to a static ‘offline’ page.

If there was a major outage or failure or the proxy is being changed the DNS records might be updated to point at static outage pages somewhere.

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Have you ever seen stackoverflow et all when the servers are down?

First, servers down would mean requests go unanswered. T His is NOT a problem solved in the 90s - it is a problem solved n the 60 so or so and server down (not answering) is part of the TCP specs. Them having problems would be an epic failure on sysadmin and web server and operating system programmer side.

Second, stackoverflow etc. run on clusters, so your server down would mean ALL Servers and the load balancer down. OS maintenance likely is done by patching server after server, so the cluster is not down. This is not exactly rocket science - clusters are around for likely longer than you live, as are standard approaches to patch them. Rolling patches are even ow part of the Windows Server Cluster as "press button watch patches" approach.

That said, when servers do maintenance they are not DOWN - you get a nice little "maintenance mode" answer from a server doing that. Never ever seen that? I get that regularly. So, the question hardly makes sense because they are not down during routine maintenance - they are just not answering YOUR question with sensible content because the answer you get is a maintenance mode page.

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