When dealing with the administration of domains, you are often faced with the question of where to manage your domains at all. For some time now you can also use domain name registrations from AWS via Route53. However, if you have organized your domains with any other provider (Ionos 1&1, Strato, Schlundtech, Checkdomain, etc.) and are now planning to switch to another domain provider (like AWS Route53) then you need to keep the following in mind to avoid off-line times reduced.
Domain records are always cached. And that, depending on the configuration, between a few minutes and several days. Domain providers like to set the nameserver entries of their own name servers to high values (for example, 48 hours, as with NS entries from Ionos 1&1).
The problem: Some domain hosters **immediately** delete (in the moment were you move your domain) all entries in their name servers. This procedure is problematic because time elapses between deletion of the DNS entries (with the old provider) and the grasping of the entries from the new provider (for example Route53).
If you have saved 48 hours caching time for the NS entries (name servers) with a restrictive provider, then there is a failure of all systems (website, e-mail, etc.) for the duration of the complete domain change to AWS. To make it even more complicated now: the transfer of some top-level domain endings (.de) usually go fast, but other domain endings can take a long time.
Therefore, one should set the TTL for the name servers to a low value at least a few days before moving a domain, in order to minimize downtime for end users.