The SOA record is the mandatory and most important entry in every DNS zone. It acts as an administrative passport, defining how multiple servers synchronize data, when to recheck updates and how to behave during failures. Most users never see SOA because hosting manages it automatically, but understanding it is essential when solving complex DNS issues.
The full name Start of Authority means responsibility for this part of DNS begins here. SOA must be unique within the zone and always sits at the zone apex.
SOA fields
The first field is the primary name server hostname. The second is the responsible administrator email in a special form โ the "@" symbol is replaced by a dot, so "admin@sayt.uz" becomes "admin.sayt.uz".
The remaining fields are technical: serial is the zone version, refresh is how often secondaries poll primary, retry is the wait time on failure, expire is how long secondaries keep serving data when primary is unreachable, and minimum TTL is the default caching value.
Serial number and zone sync
Serial is the most actively changing field. Each time a record is edited, serial is incremented. Secondary DNS servers regularly query primary and reload the zone whenever serial grows.
Many admins use the YYYYMMDDNN format such as "2033021201" โ February 12, 2033, change number 01 for that day. The format is not required, but serial must always increase between changes.
Refresh, retry and expire in practice
Refresh is typically 3600 to 86400 seconds. Smaller values propagate changes faster but increase load on primary.
Retry is the wait time when primary is unreachable, usually 600 to 1800 seconds. Expire is the most critical value: if primary stays down longer than this, secondaries stop serving the zone. A week is the common choice.
Negative caching and minimum TTL
Modern DNS uses minimum TTL primarily for negative caching: when a resolver learns a name does not exist, it caches that negative answer. Minimum TTL defines how long that cache lives.
Values of 300 to 3600 seconds are typical. Too small a value over-queries your server, too large delays the appearance of newly added subdomains.
Sayt.uz practice
Our DNS automatically provisions SOA with refresh 3600, retry 600, expire 1209600 (14 days) and minimum TTL 300. In our experience these values are optimal and 99.7 percent of customers never change them.
Manual SOA editing is available only by request through our administrators because wrong values break the whole zone. Specialist consulting starts at 100 000 soum and a full DNS audit at 250 000 soum. A .uz domain costs 119 000 soum per year with standard SOA and DNS management included.