Testing CAST AI on GKE: A Hands-On Kubernetes Workload Optimization Lab

Kubernetes makes it easy to define CPU and memory requests for our applications. But there is a problem: How do we know whether those resource requests are actually correct? If an application requests: yaml resources: requests: cpu: "1000m" memory: "1Gi" but normally consumes only a few millicores of CPU and a few megabytes of memory, we may be reserving significantly more cluster capacity than the workload actually needs. I wanted to understand how Kubernetes cost optimization platforms detect this situation, so I built a small hands-on lab using: Google Kubernetes Engine (GKE) CAST AI Kubernetes Docker FastAPI Google Artifact Registry The goal wasn't simply to install CAST AI. I wanted to observe the complete process: Deploy workload ↓ Observe resource usage ↓ Compare requests vs usage ↓ Identify over-provisioning ↓ Generate recommendation ↓ Apply rightsizing ↓ Verify from Kubernetes Architecture The lab architecture was intentionally simple. FastAPI Coffee API | v Docker Image | v Google Artifact Registry | v GKE Cluster | v Kubernetes Deployment | +----------------+ | | v v Pod #1 Pod #2 | | +-------+--------+ | v ClusterIP Service + | v CAST AI | +-------+-------+ | | v v Cost Monitoring Workload Optimization 1. Building a Small Test Application I created a very small FastAPI application for the experiment. from fastapi import FastAPI import socket import os import time app = FastAPI() @app.get("/") def home(): return { "message": "Coffee Shop API", "hostname": socket.gethostname(), "pod": os.getenv("HOSTNAME"), "time": time.time() } @app.get("/coffee") def coffee(): return { "coffee": "Cappuccino", "price": 120 } The hostname in the response was useful later because I could see which Kubernetes Pod handled each request. 2. Containerizing the API The application was packaged using Docker. FROM python:3.12-slim WORKDIR /app COPY requirements.txt . RUN pip install --no-cache-dir -r requirements.txt COPY app.py . EXPOSE 8000 CMD ["uvicorn", "app:app", "--host", "0