Cross-zone load balancing is a crucial technique in cloud environments for distributing traffic across multiple availability zones (AZs) to enhance redundancy and reliability. While traditional load balancers focus on routing within a single AZ, cross-zone load balancing allows for more efficient use of resources by considering all available zones, as exemplified by AWS's default setting for new Application Load Balancers. This approach ensures that traffic is evenly distributed across instances in different zones, improving load management and mitigating the risk of overloading individual resources. Tools like Gremlin can help validate whether cross-zone load balancing is enabled and functioning correctly by providing automated reliability tests and monitoring services to detect potential risks. For more complex scenarios, such as cross-region load balancing, additional services like AWS Route 53 can be used to connect multiple load balancers and ensure traffic is routed to healthy endpoints. Gremlin also offers a suite of experiments to simulate various failures and test system resilience, helping teams identify and address availability risks proactively.