~ dns guide

DNS TTL Explained

TTL means Time To Live. It tells recursive resolvers how long they can cache a DNS answer before asking again. During migrations, TTL is often the reason one user sees an old answer while another sees the new one.

What TTL Controls

• How long a resolver can reuse a cached answer.
• How quickly record changes may become visible after caches expire.
• How much query load authoritative DNS servers receive.

Before A Migration

Lower TTL before the change window when you can. Lowering it after the change does not clear caches that already stored the old longer TTL.

When To Use Propagation Checks

Use DNS Propagation when you need to compare resolver answers and decide whether users are seeing cache delay, bad delegation, or an authoritative DNS problem.