Why changes take time.
WHAT TTL IS
How long a record may be cached before being checked again.
Set per record.
WHAT THAT MEANS
After you change a record, resolvers holding the old value keep it until their copy expires.
WHY IT LOOKS INCONSISTENT
Different resolvers cached at different times.
Some serve the new value immediately; others serve the old one for hours.
WHAT PROPAGATION ACTUALLY IS
Not a spreading process.
It is caches expiring at different times.
HOW TO MAKE A CHANGE SMOOTHLY
Lower the TTL well in advance Wait for the old TTL to pass Make the change Raise the TTL afterwards
WHY IN ADVANCE
Lowering the TTL only takes effect once the old value expires.
WHAT A SENSIBLE TTL IS
Longer for stable records, shorter before a planned change.
WHAT TO AVOID
Very short TTLs permanently, which add lookups Changing records repeatedly during a migration
WHAT TO CHECK
What the current TTL is, before planning a change.
