How to quickly restore the availability of the site for users?

Question

Domain Name System

How to quickly restore the availability of the site for users in case of hosting failure, if there is a site mirror on another hosting?
DNS servers are located in the third place and work properly.
I understand that it is necessary to configure the DNS server, do you need advice on what to look for and in which direction to dig? Add A Recording Mirror?

Answer 1

There are different options, from using dns to cloudflare, for example (updating dns with default ttl is very fast around the world) and self-made monitoring, which will switch the A record to the working site through the API.
Use load balancers with configured active-passive logic.
You can also manually switch the A record.

Answer 2

in fact, you just need to change A record to a new server
if there is no downtime at all - you need to use DNS that can Round-Robin