Beyond 'It Works on My Machine': Solving Docker Networking & DNS Bottlenecks

Beyond "It Works on My Machine": Solving Docker Networking & DNS Bottlenecks in Production You've been there. Your staging environment is green. Your local Docker Compose setup is flawless. But the moment you hit 50% traffic in production, your logs start bleeding EAI_AGAIN and ETIMEDOUT errors. The culprit? It's rarely your code. It's the silent, often misunderstood layer of Docker Networking and DNS resolution. In this guide, we're going deep into the production-grade networking issues that plague high-traffic applications. We'll cover why your DNS lookups are failing, how to optimize container-to-container communication, and how to fix the dreaded MTU mismatch that kills packets on AWS. 1. The DNS Resolution Trap: ndots and Search Domains When a container tries to resolve api.internal.service, it doesn't just ask the DNS server once. Because of how Linux handles DNS, it might ask five times. The Problem: DNS Amplification By default, Docker (and Kubernetes) sets ndots:5 in /etc/