Service Mesh Performance Costs: The Reality of Sidecar Latency

Introduction

Your service handles 2ms p99 latency. You adopt Istio for zero-trust security and traffic management. Six weeks later, on-call engineers are staring at 11ms p99. The architecture didn’t change. The code didn’t change. Only the mesh did. This is the tax every team pays when they deploy a sidecar proxy, and understanding exactly where that tax comes from — and when it’s worth paying — is what separates architects who build resilient systems from those who debug them forever.