Using a primary database with multiple read replicas allows the application to handle a high volume of read operations by distributing the read traffic across the replicas, thus reducing load on the primary instance and ensuring high availability and low latency for read operations. Read replicas are particularly effective in read-intensive environments. Multi-AZ deployment is beneficial for high availability but does not inherently distribute read operations. Write-through caching is used to ensure data integrity between the cache and the database, focusing on write operations, not reads. Sharding is useful for both read and write operations but would require complex data distribution to manage read traffic.