The 80/20 Rule of Kubernetes Cost: Stop Obsessing Over Micro-Optimizations

I see teams waste weeks trying to shave 2% off their bill by optimizing serialization formats or tweaking garbage collection settings.

Meanwhile, their clusters are running at 15% utilization.

In Kubernetes cost optimization, the Pareto Principle (80/20 rule) is brutally effective. 80% of your wasted spend comes from just two sources.

1. The “Just in Case” Buffer (Requests)

Engineers are risk-averse. If an app needs 200m CPU, they request 1000m “just to be safe.”

Kubernetes reserves that 1000m on the node. It cannot be used by anyone else, even if the app is idle.

The Fix: Look at your Max Usage over the last 7 days. Set your Request to Max Usage + 20%. That’s it. You just saved 60% of your capacity without touching a line of code.

2. The “Lazy” Node Type (Rightsizing)

“We use m5.2xlarge because that’s what we’ve always used.”

If your pods are memory-heavy (Java, Python), running them on Compute Optimized (c5) nodes is throwing money away. You’ll run out of RAM while half your CPU sits idle.

The Fix: Bin-packing. Look at your aggregate cluster requirements.

• High CPU / Low RAM? -> Use c6i or c7g (Graviton).
• High RAM / Low CPU? -> Use r6i or r7g.

Matching your node shape to your workload shape is the single biggest infrastructure win you can make.

The Other 20% (The Distractions)

Things that matter less than you think:

• Spot Instances: (See my other post). Great, but high effort and engineering risk.
• Storage Tiers: Unless you’re storing petabytes, EBS costs are usually a fraction of compute.
• Network Transfer: Important, but often hard to fix without re-architecting.

The Strategy

If you want to cut your bill in half, follow this order of operations:

1. Week 1: Right-size Requests. (Low risk, high reward). Use a tool like ClusterCost to find over-provisioned pods.
2. Week 2: Right-size Nodes. (Medium risk, high reward). Move workloads to node types that fit their profile.
3. Week 3: Everything else.

Don’t let perfect be the enemy of profitable. Fix the big leaks first.