For this, simply set up the Roblox side first, and make a basic voting system. Afterward, you will need to create an external server so you can communicate with it, you will need to send a post request to your server when someone votes and then get the newest vote from the Roblox servers. Then just display the newest vote in each server.
This is definitely NOT necessary. I believe this person is informed. Instead you can use MessagingService, to communicate between servers. It’s very easy to learn, you can pick it up quickly.
I think you could also rely on memory stores, for storing the votes of each map, having the correct number of votes in a really fast pace. Check it out : Memory Stores | Documentation - Hub Création Roblox.
It basically works like the datastores you know, but are much faster. The problems I’d see using those could be the limited amount of data you can use and their lifetime (around a month I think). Everything is written in the link if you need to know more.