Comment by nitinag

Registrars provide the nameservers you give them to the TLD itself. So, resolution doesn't depend on the registrar's infrastructure unless you're using the registrar's nameservers directly.

It works like this: Root -> TLD -> NS -> NS -> ETC.

Root Servers are fixed and everything drills down from there: https://www.iana.org/domains/root/servers

A visual example of how the nameserver hops work starting from the root using the nameserver delegation view feature of our dns lookup tool: https://www.misk.com/tools/#dns/[email protected]...

(Disclosure: I work @ Misk.com, an ICANN accredited registrar, our link above)