[echelon]

> Is that really a thing, with HNers of all people?

You want it to be hitless. Unfortunately DNS can take days to fully propagate and you may not see mistakes until it's too late to fix them. This can cause horrifying outages.

HNers should be respectful of DNS changes and plan accordingly.

[neurostimulant]

I always setup a reverse proxy on the old server that tunnel all TCP traffics on port 80 and 443 to the new server whenever I migrated a website for this reason. Some network really take their time updating their DNS cache, even if your domain has low TTL.

[zakki]

You can change your DNS TTL to let say 5 minutes before you move to new IP. You can change it 3 days before the movement(?).

[scott_w]

A story from 10 years ago providing services to the education sector:

I did exactly what you suggested, even leaving extra time (a full weekend!) for the DNS changes to propagate. What happened?

Turns out local authorities don't all respect DNS TTL settings and we had a major outage. I had to on-the-fly learn how to configure iptables to act as a proxy for the new server.

The "proxy" was still receiving requests 2 weeks later.

[chillfox]

Fewer and fewer places actually respect DNS TTL.

[lloydatkinson]

Indeed, not sure what the anger in their comment was for.