I am wondering whether a new domain registration will become available at the exact same moment for everybody?
Because a new domain registration will not have DNS records set up already; I assume no caching will occur. Thus one would think that globally the domain's DNS records will become available at the exact same moment.
However I could not find any definite answer to my question; and would like to know for sure whether my theory mentioned above is correct.
Hoping somebody can tell me for sure!
at the exact same moment for everybody?
Yes and no. At the exact same moment for all registrars in most cases yes.
But you are not saying which TLD you are working with, and this makes a huge difference.
First not all TLDs are using registrars. Second some TLDs are using specific measures for domains about to be deleted and released to the "public", like pre-ordering list or specific catch-up servers to which the registrars need to connect, etc.
Because a new domain registration will not have DNS records set up already; I assume no caching will occur.
This is not clear. A domain name not existing is also something put in cache, it is an NXDOMAIN return code and is put in cache in resolvers for a period up to the negative TTL which is an element present in the SOA field of the parent (TLD).
This is in fact a cause of major problems as some people do test, see the domain does not exist, then register it and then do not understand why they do not see it "immediately". Others may see it immediately, but they may not because they "polluted" the cache of the recursive DNS server they are using.
globally the domain's DNS records will become available
Hence no, for the reasons above: various caches around the world may have cached the NXDOMAIN reply.
I think you are confusing registration with publication. A name can be registered but not published at all. It is also registered at time T but can only be seen somes times later depending on the various caches' content.