Creating read replicas of the primary database instance allows for the distribution of the read query load, helping to maintain query performance during traffic peaks without a costly scaling of the primary instance. This technique improves read throughput at a lower cost compared to scaling up the primary instance or using a caching service for queries that cannot be cached. Implementing read replicas is more appropriate for balancing read traffic than using a caching service, which is mainly beneficial for frequently accessed immutable data, or leveraging an additional standby replica, which is more focused on high availability rather than read distribution.