How to migrate a website with zero downtime

Migrations scare people because they picture the site going dark. Done right, nobody notices.

The process

1. Stage a full copy on the new host and test it on a temporary URL.
2. Lower DNS TTL a day ahead so the switch propagates fast.
3. Freeze content, do a final sync of the database and uploads.
4. Point DNS to the new host; the old one keeps serving until propagation finishes.
5. Issue SSL, verify email/DNS records, and monitor.
6. Keep the old host live for a few days as a safety net.

The result: a clean cutover, no broken links, no lost orders, no downtime.