There’s a kind of quiet that feels normal—until it isn't.
In Kubernetes, that silence can get expensive. Especially when it turns out your services stopped talking to each other... and no one noticed.
Worse? Sometimes you cut the connection without realizing it.
This is a story about good intentions, bad assumptions, and two outages that started with silence—and ended with expensive lessons.
The First Cut: Isolation Gone Wrong
At TechCorp—a fast-growing startup with big uptime goals and even bigger AWS bills—the Dev team rolled out a new network policy. The idea was simple: lock down backend services so only frontend traffic could reach them.
Tighter security. Fewer risks.
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: allow-frontend
namespace: production
spec:
podSelector:
matchLabels:
app: backend
ingress:
- from:
- podSelector:
matchLabels:
app: frontend
Looked clean. Deployed smooth. Broke everything.
The policy only allowed traffic from frontend pods. That meant everything else—metrics scrapers, health checks, internal testing tools—got shut out. The backend stopped getting probed. It was marked "unhealthy" by upstream systems and effectively quarantined.
No traffic. No alerts. Just… silence.
Customers were the first to notice. By then, the team was already $10,000 in the hole.
What went wrong? A missing rule in the policy. But the deeper issue was this: no one asked which systems actually needed access. Devs built in a vacuum. And production paid the price.
The Second Strike: Testing Without Sight
After that first outage, the team got cautious. Next rollout? They tested everything in staging.
This time, the focus was on egress—blocking outbound traffic from some pods:
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: restrict-egress
namespace: staging
spec:
podSelector:
matchLabels:
app: web
egress:
- to:
- podSelector:
matchLabels:
app: api
Goal: stop web apps from calling stuff they shouldn’t.
What they missed? Those same apps needed to pull external dependencies during CI/CD builds.
The result: broken builds, failed pipelines, and confused engineers chasing ghosts. It took hours to trace the issue back to the new policy.
Final damage? About $8,000 in lost time, delayed deploys, and broken SLAs.
And again, no alerts. No warnings. Just a system that stopped talking.
When Silence Isn’t Golden
So what caused both outages?
Not Kubernetes. Not the tools. Not even the policies themselves.
It was people. Working in isolation. Making assumptions. Rolling out changes without a shared mental model of how the system fit together.
Because when Dev can’t talk to Prod—and monitoring can’t talk to anything—your platform’s flying blind.
What Could've Helped
The tools were there. Just underused.
- Network policy previewers like Cilium Hubble: to simulate impact before rollout.
kubectl execandpingtests: to verify pod-to-pod connectivity.- Prometheus/Grafana: to trigger alerts on traffic drops between services.
- Helm hooks: to validate network reachability during deployments.
- Terraform planning: to catch infra changes in PRs—before they ship.
But the biggest fix?
Bringing everyone to the table. Devs. Ops. Security. No one flies solo when it comes to network access.
A Few Hard-Learned Rules
Network policies are like firewalls. Powerful, but easy to misuse.
Here’s what the team does now:
- List out service dependencies—both ingress and egress—before writing policies.
- Test actual traffic flows in staging with real workloads.
- Set alerts for dropped packets, sudden silences, or service isolation.
- Make reviews cross-team. No more silos.
Because silence isn’t just dangerous—it’s expensive.
TL;DR
- Two network policy changes led to ~$18,000 in downtime and delays.
- In both cases, teams acted alone—without a shared map of service needs.
- The right tools existed. But weren’t used early enough.
- Clear, cross-team communication isn’t a nice-to-have. It’s essential.
"If your devs can't reach prod, it's only a matter of time before no one reaches your customers."