Edge Stack is an API gateway that handles north-south traffic from external clients into a Kubernetes cluster, providing routing, protocol translation, security, and API management capabilities. Istio's service mesh handles east-west traffic between services within the cluster, offering features like service discovery, traffic management, resilience, security, and observability. Together, Edge Stack and Istio provide defense-in-depth for the entire application, isolating failures, and enabling end-to-end observability and visualization of service dependencies. Implementing this combination empowers development teams to confidently build and deploy microservices, ensuring their applications are secure, reliable, and observable at every level.