Ensuring zone redundancy is crucial for maintaining service resilience in the face of data center outages, as simply deploying across multiple zones does not guarantee resilience to zonal failure. Even minor issues, such as slight packet loss, can escalate into significant problems, underscoring the importance of thorough testing. To effectively test redundancy, it's vital to simulate load and network failures, ensuring that services can handle increased demand when a zone goes offline. Over-provisioning is recommended to maintain service integrity during outages, as reactive autoscaling may not suffice when multiple services are affected simultaneously. Additionally, proper configuration is necessary to prevent issues like cross-zone traffic to failed dependencies from causing increased error rates. Validation involves testing under load conditions that mimic real-world scenarios to ensure that services are not only redundant in theory but also in practice, requiring careful management of scaling mechanisms and traffic distribution.