What is a good default DNS TTL?

3600 seconds (1 hour) is a good balance between caching efficiency and reasonable update speed. For critical services, consider 300–600 seconds.

Should I set TTL to 0?

Not recommended. TTL=0 means every request triggers a fresh DNS lookup, increasing latency and load on DNS servers. Most resolvers enforce a minimum floor (30–60s) anyway.

How should I lower TTL before a migration?

At least 24–48 hours before the change, lower the TTL to 300 seconds. This ensures old cached records expire quickly once you update the record.

DNS TTL Best Practices — Optimal Values for Every Scenario

Learn how to choose the right DNS TTL value for performance, reliability, and fast failover.

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Problem

You’re unsure what TTL to set for your DNS records, or you’re planning a migration and need to minimize downtime.

TTL Cheat Sheet

Scenario	Recommended TTL	Reason
Normal operation	3600s (1h)	Good cache hit ratio, reasonable freshness
Pre-migration (24–48h before)	300s (5min)	Ensures fast propagation after change
During failover/incident	60–300s	Rapid switching if needed
Static records (rarely change)	86400s (24h)	Maximum caching, minimal DNS queries
CDN/load balancer targets	300–600s	Balance between caching and flexibility

Top 3 Mistakes

Leaving TTL at 86400 before a migration — Old records stay cached for up to 24 hours after the change.
Setting TTL to 0 — Most resolvers ignore it (minimum 30–60s), and it increases unnecessary DNS load.
Forgetting to restore TTL after migration — Low TTL kept permanently wastes resolver resources and increases latency.

Diagnosis with DechoNet

DNS Lookup — Check the Records tab to see current TTL values for each record type.
Compare TTL across A, MX, and NS records to ensure consistency.

Resolution Checklist

Set default TTL to 3600s for most records.
Lower TTL to 300s at least 24–48 hours before any planned DNS change.
Make the DNS change and verify propagation with multiple resolvers.
After confirming propagation, restore TTL to its normal value (3600–86400s).
For critical services, keep TTL at 300–600s for rapid failover capability.