Porkbun's DNS defaults to a 600-second TTL, which is shorter than the one-hour default some larger registrars use. That means a resolver will only hold a cached answer for about ten minutes before checking again, so editing an A record or adding a TXT string on Porkbun usually becomes visible fairly quickly across most locations. You can shorten the TTL further for a planned change, or raise it once things are stable to reduce load.
The exception, as everywhere, is changing your domain's nameservers — moving DNS management to or from Porkbun's default nameservers. That delegation is cached by the TLD registry and can take up to a day or two to propagate fully, regardless of how short your record TTLs are. If you are pointing the domain at an external host's nameservers, plan for that longer window and keep records consistent during the transition.
Porkbun also offers a straightforward interface with sensible defaults, so most propagation questions come down to the TTL you can see next to each record. If a change is not showing after well past the TTL, check that the domain is still using Porkbun's nameservers and that you edited the record under the correct domain, rather than assuming the delay is normal.