TTL

TTL (Time to Live) is a value on every DNS record that tells DNS resolvers how long to cache the record before checking for an update. A TTL of 3600 means the record is cached for 1 hour. Low TTLs (60-300 seconds) mean changes take effect quickly but generate more DNS queries. High TTLs (86400 seconds = 24 hours) reduce DNS traffic but mean changes propagate slowly. Before making DNS changes, it is common practice to lower the TTL in advance so the old record expires quickly from caches worldwide.