TTL (Time To Live) is the time in seconds a DNS record “lives” in intermediate resolver caches. After TTL passes, a resolver re-asks your NS for a fresh value.
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Common values
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- 300s (5 min) — very fast propagation, higher DNS load
- 3600s (1 h) — balanced. Standard for most domains
- 14400s (4 h) — light load, medium propagation
- 86400s (24 h) — low load, slow propagation
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When you need low TTL (300–600)
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- Preparing to change server or host — changes should propagate in 10 min
- Using failover (one IP down → switch to backup)
- Dynamic DDNS setups
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When high TTL (3600+) is fine
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- Stable site with no plans to change infrastructure
- Want fewer DNS queries and faster response
- Stable NS, MX, TXT
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Migration strategy
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- A day before: lower TTL to 300
- Wait for the old TTL (e.g. 3600 = 1 h) — all caches update
- Do the migration — changes propagate in 5 minutes
- After stabilization: raise TTL back to 3600