Network & Infrastructure / DNS, DNSSEC & Service Discovery
TTL reduction timing before a DNS migration
A service migration lowers a record's TTL at the same moment it changes the address, yet old endpoints still receive traffic. Existing caches can retain the previous longer lifetime.
Environment and inputs: Authoritative and recursive DNS infrastructure; BIND examples are conceptual and require release-matched configuration. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Record the old TTL, the time it was lowered, authoritative publication and observed cached remaining lifetimes. Include dependent aliases, negative entries and application-level caching where relevant.
Explain the result
A new TTL governs newly obtained data; it does not rewrite records already cached elsewhere. A cutover can therefore have a longer transition than the freshly published value suggests.
Plan the fix
Lower TTLs sufficiently ahead of the move, keep both endpoints serviceable during overlap and define application rollback behavior. Avoid promising instantaneous DNS-based failover.
Check the result and rollback
Observe traffic to both old and new endpoints through the planned window and verify dependencies independently. Restore the old answer if the new service fails, accounting for caches holding both generations.