What Is the Time Delay for Primary/Standby Replication?

If the replication thread is running properly, replication latency is a value measured in seconds. Replication latency is NULL if the SQL thread is abnormal, or if the I/O thread is running properly but the SQL thread has applied all relay logs.

The delay for primary/standby replication cannot be calculated using a formula as the delay is affected by the following factors:

• Network communication status
• Transaction workload on the primary DB instance in transactions per second (TPS)
• The size of the transaction executed by the primary DB instance (this affects the duration of transaction executions)
• Loads on the standby instance and read replicas

If the primary DB instance is under heavy load for a period of time and executes a large number of transactions per second, replication to the standby DB instance will usually be delayed. Otherwise, the replication delay is generally in seconds.

RDS for PostgreSQL: To check data consistency between the primary and standby DB instances, view Replication Lag on the Cloud Eye console to obtain the value of the primary/standby replication delay.