Built a lightweight Prometheus tool to rightsize CPU/RAM

Nikolai — Wed, 25 Feb 2026 10:15:11 +0000

I recently had to urgently optimize resources across 200 servers in our environment. Our cloud provider doesn’t offer any built-in rightsizing or capacity optimization tools, and I couldn’t find a simple open-source solution focused specifically on CPU/RAM rightsizing based on Prometheus metrics.

The goal was simple:

Analyze historical usage
Calculate realistic resource requirements
Identify reclaimable CPU cores and RAM
The tool:
Pulls metrics from Prometheus
Calculates p95 CPU usage (non-idle cores, summed per instance)
Calculates p95 RAM usage
Applies a configurable safety margin (default 20%)
Ensures CPU minimum = 1 core
Rounds RAM to 0.5 GB
Generates:
Reclaim recommendations
Grow recommendations (if under-provisioned)
Provides a simple web UI to explore:
Total reclaimable CPU/RAM
Per-job breakdown
Per-host details
It supports:
Linux (node_exporter)
Windows (windows_exporter)

Architecture is intentionally simple:
Prometheus → Analyzer → JSON → FastAPI → Web UI
It’s not meant to replace full FinOps platforms — just a focused, practical tool for teams already using Prometheus.

GitHub: https://github.com/grachamba/prom-analyzer
Looking for feedback
Does the p95 + safety margin approach make sense in your environments?

DEV Community: Nikolai

Built a lightweight Prometheus tool to rightsize CPU/RAM