Availability zones are logical data centers within a cloud region that are isolated and independent from each other. Availability zones have their own power, cooling, and networking infrastructure, and are connected by low-latency networks. Availability zones help to ensure high availability and fault tolerance for cloud applications by allowing customers to deploy their resources across multiple zones within a region. If one availability zone experiences an outage or maintenance, the other zones can continue to operate and serve the application.
To ensure the CSP does not bring both servers down for maintenance at the same time, the cloud administrator must configure the application to use availability zones. The administrator can deploy the two database servers in different availability zones within the same region, and enable replication and synchronization between them. This way, the application can access either server in case one of them is unavailable due to maintenance or failure. The administrator can also use load balancers and health checks to distribute the traffic and monitor the status of the servers across the availability zones.