The rules behind every plan

1. TTL: the memory of the internet

Every DNS record carries a TTL ("time to live") in seconds. A resolver that looked up your domain keeps that answer for up to the TTL before asking again. If your records say 14400 (4 hours), some visitors keep reaching the old server for up to 4 hours after you change the address.

So the plan lowers the TTL to 300 seconds first. That only works if it is done at least one old TTL before the switch, because the old, long TTL is still in resolvers' memory. FastHostNow adds an hour of margin:

deadline    = switch - (old TTL + 1 hour)
recommended = switch - max(48 hours, old TTL + 1 hour)
earliest clean switch (if the deadline passed) = now + old TTL + 1 hour, rounded up to the hour

After the move the TTL goes back up (3600 is a common choice) 48 hours later.

2. A record or nameservers

A record change: your DNS stays where it is and you change the address the domain points to. With a 300-second TTL almost everyone follows within minutes.

Nameserver change: the new host takes over your DNS. The registry for .com and .net publishes nameserver records with a 2-day TTL that you cannot lower, so for up to 48 hours some resolvers keep asking your old DNS host. The plan therefore changes the A records in the OLD zone to the new address at the same moment, copies every record (MX and TXT included) to the new zone first, and keeps the old host 14 days.

3. Freeze and final copy

A site with a database keeps changing: posts, comments, orders, sign-ups. Anything written to the old server after the last copy is lost. The plan freezes changes 60 minutes before the switch (120 for a shop, with orders paused), takes a final database copy 30 minutes before, and switches. Plain-file sites need no freeze.

The first full copy happens 3 days ahead (5 days for sites over 20 GB) so that the final copy only moves what changed.

4. Email

If email stays at Google, Microsoft or another provider, nothing about it should change. The danger is a new DNS zone without your MX, SPF, DKIM and DMARC records: the plan adds that check.

If mailboxes move with the site, they are created on the new host and copied over IMAP two days ahead, then once more 72 hours after the switch to pick up mail that stale DNS delivered to the old server.

5. Certificates

Free certificates (Let's Encrypt, cPanel AutoSSL) can usually only be issued once the domain points at the new host, so HTTPS may need a few minutes after the switch. A bought certificate can be installed in advance.

6. After the switch

Check from a phone on mobile data (your own network may still remember the old address), keep a rollback decision point an hour in, and keep the old account 7 days (14 after a nameserver change, a shop move or a mail move). Take one last backup before cancelling.

These are planning rules of thumb from how DNS caching works. Hosts differ; their own migration instructions win where they disagree.