You plan to deploy hundreds of microservices on GKE. Which managed solution should you use to secure inter-service communication with mTLS?

Anthos Service Mesh (ASM) is the correct choice because it's Google Cloud's fully managed service mesh solution, built on Istio. It provides robust features for securing inter-service communication, including automatic mTLS, policy enforcement, and traffic management, which are essential for hundreds of microservices. Deploying open source Istio is a viable option, but it requires more operational overhead for management and upgrades compared to the fully managed ASM. Global HTTP(S) Load Balancing with managed SSL certificates secures traffic to your services from external clients, not between your microservices within the cluster. Installing cert-manager on GKE automates certificate renewal but doesn't provide the comprehensive service mesh capabilities like mTLS for inter-service communication that ASM offers.