DNS Troubleshooting & Caching — Stop Blaming Your Network

🛠️ DEVOPS TIP — Aug 13, 2026

DNS Troubleshooting & Caching — Stop Blaming Your Network

The problem: Your app can't reach an API by hostname. nslookup shows a stale record. Frontend blames backend, backend blames DNS, ops blames everyone.

DNS is a chain of resolvers — each with its own cache and TTL:

• systemd-resolved stub (127.0.0.53)


• Docker embedded DNS


• Go runtime in-process cache

Real commands that actually help:

# Check what your system thinks DNS is:
resolvectl status
getent hosts example.com

# Compare upstream vs cached:
dig @8.8.8.8 example.com
dig @127.0.0.53 example.com

# Flush your local DNS cache:
resolvectl flush-caches

# Trace the full resolution chain:
dig +trace example.com

Quick fixes:

• Docker: add dns 8.8.8.8 to your container config


• Kubernetes: use CoreDNS forward zones for internal services


• systemd-resolved: FallbackDNS=8.8.8.8 1.1.1.1 + Domains=~company.local

💡 Pro tip: Reduce attempts from 4→2 in systemd-resolved to cut DNS outage hang from 16s to 4s.