What is the maximum number of third-level subdomains?

Question

Domain Name System

Hello!
I am interested in the question, what is the maximum number of third-level subdomains that one domain can have? Does this amount depend on something (server specifications, hosting company rules, etc.)?
For example, there is a domain: site.com.
How many third-level subdomains can it have:
3lvl subdomain 1 .site.com,
3lvl subdomain 2 .site.com,
3lvl subdomain 3 .site.com,
3lvl Subdomain N .site.com
I am not interested in the total number of domain levels, such as NlvlSubdomain...........3lvlSubdomain.site.com. I know there is a character limit there.

Answer 1

There is absolutely no limit. If I'm not confused, then according to combinatorics: the maximum number of characters in the domain is approximately the 36th degree (or how many digits of letters and characters are possible in total).
To be convinced of this, it is enough to look at ucoz, narod and others, there are a lot of them.

Answer 2

Strictly speaking limited.
The size of the file system on which the zone file is stored (and free space there).
This restriction will work faster than the one about combinatorics.
Well, do not forget that the resolution speed in such a zone will be sad (you need to read the zone file, if it does not fit into the server's memory, read it from the disk).