Cloud SQL Read Replicas for Scaling Read-Heavy Workloads

Quick Answer

The answer is to add read replicas across zones. This configuration is correct because Cloud SQL read replicas use asynchronous replication to maintain a copy of the primary instance, allowing you to offload read-heavy workloads by distributing SELECT queries across multiple replicas. By placing replicas in different zones, you also gain high availability and fault tolerance, ensuring that read capacity remains resilient even if one zone experiences an outage. On the Google Professional Cloud Developer exam, this scenario tests your understanding of scaling strategies for managed databases—specifically that read replicas scale reads horizontally, while vertical scaling (increasing machine size) is less efficient for read-heavy patterns. A common trap is confusing read replicas with failover replicas; remember that failover replicas are for high availability, not for scaling read traffic. Memory tip: “Read replicas read, failover replicas fail over.”