Round Robin records are records with the same name value that point to different IP addresses or different Fully Qualified Domain Names. For instance, you can have the domain domainexample.com pointing to the IPs 188.8.131.52 and 184.108.40.206 simultaneously. This means that, if you query the domain domainexample.com, there is a 50% chance that the host 220.127.116.11 will respond to that request.
Let's use user.domain.com as an example. Below you can see that the A record for the user.domain.com points to three different IP addresses.
Record point to IP
Now we have three users that are visiting the domain user.domain.com. When user one asks for the domain, they will be pointed to for instance, IP #1. The second user will be served with the domain content by IP #2 and so on. This is a rotation process, considering that the IPs have been configured to receive traffic equally for that specific record and taking into account the record is not cached in any of the user's systems.
Why consider using Round Robin
Round Robin can provide redundancy for your domain. In case one of the IPs the domains points to is no longer available, downtime can be avoided if you have an alternative IP that will still handle your DNS traffic. This is very cost effective to ensure that users are still able to access your domain.
2. Resource prioritization
If you have a server with higher processing power that can handle more DNS queries, or if you simply would like to spare it from any type of work overload, you can user Round Robin to prioritize your resources based on your needs.
3. Load Balancer
Round Robin will allow you to configure the percentage of traffic you would like to have handled by different resources. Many services offer what we call weighted Round Robin, which enables the set up the frequency in which a server will be queried at the authoritative DNS level. Round Robin is very beneficial when useful when an endpoint is being overwhelmed with loads of traffic.