DNS changes during a migration
DNS changes are not seen everywhere at exactly the same moment. Authoritative records, resolver caches and application caches can affect what a user reaches. Plan a period in which the old and new endpoints may both receive traffic.
Before changing records
- Identify the authoritative DNS provider and export or record the existing zone.
- Review website, mail, verification and certificate-validation records; changing nameservers affects more than the website.
- If using a lower TTL for cutover, change it early enough for the previous TTL to expire.
- Validate the destination and decide how to avoid writes diverging between old and new systems.
After cutover, check authoritative records, several independent resolvers and the application itself. Keep a documented rollback, and do not delete the previous environment immediately. Coordinate any required DNS updates with your current DNS provider and keep access to the domain account available during the migration.
