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/re