🌐 What is TTL in DNS?
TTL (Time to Live) in DNS is the time (in seconds) that a DNS record is cached before checking for updates from the authoritative DNS server. It helps reduce DNS queries and speeds up website access.
🕒 Example: If TTL is 3600 seconds (1 hour), your computer will remember the DNS record for 1 hour before requesting a fresh one.
✅ When to Use High TTL (⏳ Long Cache Time)
Use a high TTL (e.g., 86400 seconds = 24 hours) when:
🔹 The DNS record rarely changes (e.g., static websites, email servers).
🔹 You want faster DNS resolution and reduced DNS queries.
🔹 The service is stable and does not require frequent updates.
🎯 Example: A company's main website that doesn’t change hosting often.
🟢 Pros: Faster performance, less DNS lookup load.
🔴 Cons: Slow propagation if you need to change the DNS record.
⚡ When to Use Low TTL (⏳ Short Cache Time)
Use a low TTL (e.g., 60-300 seconds = 1-5 minutes) when:
🔹 Your IP or server changes frequently (e.g., during server migrations).
🔹 You need quick failover in case of downtime.
🔹 Load balancing is required, and DNS needs frequent updates.
🎯 Example: A website behind a load balancer or a cloud service with dynamic scaling.
🟢 Pros: Faster DNS updates, better flexibility for changes.
🔴 Cons: Higher DNS query load, slightly slower initial response times.
🎤 Interview Tip 🚀
If the interviewer asks "What TTL would you recommend?", respond based on the use case:
✔️ For stable services → Use High TTL to reduce queries and improve speed.
✔️ For dynamic or failover setups → Use Low TTL for quick updates and flexibility.
🔥Pro Tip: Before major DNS changes, lower the TTL 24 hours in advance to allow for faster propagation! 🏆