How does DNS hosting work?

Question

Domain Name System

I know how a DNS name is resolved and how DNS works in general (root servers, DNS records, etc.), but there are some things I don't understand. We know that an NS server is responsible for a certain DNS namespace so that the name is resolved when we will buy a domain name this name is resolvable and belongs to our NS server. It’s not clear to me why I should additionally buy, for example, DNS hosting on cloud flare and register NS there? You will say for reliability, but if, for example, a failure occurred on the native NS server of the domain (which we bought), and at the same time, when the client performed a DNS request, naturally, the root servers will respond to this request, giving the address of the NS server that responds to that zone (that is, to the native NS), and on this server there was a failure.Question: How in this case will the root DNS server respond to requests by issuing a Cloudflare hosting NS server so that the name is resolved, and this NS is not native to the domain we bought, what will happen?

Answer 1

To support any DNS zone, as a standard, you need to have at least 2 DNS servers with this zone.
If zone management is delegated to these servers, no one else can answer queries about DNS records in that zone.
On DNS servers a level higher there will be only records where your zone is delegated and that's it.
And please, put punctuation marks and correct your text - it is difficult to read and difficult to understand.

Answer 2

Why buy additionally, for example, cloud flare DNS hosting

The domain registrar is not obligated to provide you with DNS hosting. There are a significant number of registrars without such a service, and if you do not specify the NS servers, the domain simply will not work, or even they will not let you buy it at all.
The owner of the zone has its own NS servers that set the settings for all domains in the zone. Your registrar prescribes the NS servers you specified in the zone settings. If the registrar provides the NS service, then he simply registers his NS in the zone settings.

Answer 3

on the native NS server of the domain (which we bought)

If we migrated DNS to Cloudflare (AWS, Google, another provider), then it will become native.