Istio is an open-source service mesh for Kubernetes that adds a consistent layer for managing service-to-service traffic in microservice systems, including security, policy enforcement, and observability. It works by running a small proxy next to each workload to intercept requests, while a control plane configures those proxies to apply mutual TLS (mTLS, meaning both sides authenticate and encrypt traffic), traffic routing rules, retries and timeouts, and standardized metrics, logs, and traces.
With Istio, platform teams can roll out uniform security and traffic controls and get reliable telemetry across many services from one place; without it, these concerns tend to be implemented inconsistently in each service, making incidents harder to debug and changes riskier to deploy. This gap exists because distributed calls fail in partial, unpredictable ways, and handling identity, encryption, and routing correctly is difficult to standardize in application code.