It doesn’t — that’s a myth born from lazy TTL choices. DNS ‘propagation delay’ equals the highest TTL set on the old record, unless a resolver flushes early. If your old A record’s TTL was 86400 (24 hours), some resolvers may cache it for up to 24 hours. If TTL was 300, the maximum delay is 5 minutes. Change your TTL to 60-300 seconds a day before making a change, and ‘propagation’ happens in a minute.
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