Aoi Takahashi

Posted on Jun 15

CKS Success Story -44 Days Walking with AI-

#cks #kubernetes #kubestronaut #ai

Hi! I'm Aoi! I Passed the CKS Exam — Here's My Story!

I passed the CKS exam and I'm so happy I had to write about it!

This time I asked AI to accompany me throughout my study journey, so I've added the subtitle "44 Days Walking with AI."

This article is translated from the original article written in Japanese.
https://zenn.dev/aoi/articles/5a816271cbb174

My Skill Set

7 years working with Kubernetes as an SRE
Experience with Linux server setup and administration
CKA and CKAD certified

SRE stands for Site Reliability Engineer — I work on platform maintenance (including Kubernetes) for developers. So I have a solid foundation in Kubernetes basics. Since we use AWS EKS, I rarely touch the Control Plane directly at work.

Summary

Since I had AI accompanying me, I asked it to write the summary. Here's what it came up with:

Study Period

April 21, 2026 (Tue) – June 4, 2026 (Wed) = approximately 44 days

I failed the first attempt (5/26) with 50 points, but regrouped quickly and passed on the second attempt (6/4).

Study Resources Used

KodeKloud CKS Course (video + hands-on labs)
Killercoda (killercoda.com/killer-shell-cks) — all 34 scenarios completed twice
Killer.sh (practice exam included with the certification purchase, taken twice)
Killer Shell official YouTube (full course, approximately 12 hours)
Official curriculum PDF (CKS_Curriculum_v1.34.pdf)

Study Flow

Phase 1: Input Phase (4/21–5/6)

Watched all KodeKloud video sections to build conceptual understanding of each domain.

System Hardening (AppArmor / Seccomp / kube-bench)
Cluster Setup (RBAC / NetworkPolicy / Ingress TLS / CSR)
Microservice Vulnerabilities (PSA / gVisor / Cilium / Istio mTLS)
Supply Chain Security (Trivy / SBOM / image signing / static analysis)
Monitoring & Runtime Security (Falco / strace / Audit Logs)

Golden Week (Japanese national holidays) let me get significantly ahead of schedule.

Phase 2: Hands-on Phase (4/27–5/13)

Worked through Killercoda scenarios in order. I also reviewed the official curriculum PDF myself and confirmed things like OPA Gatekeeper being out of scope — staying precise about what's actually on the exam was a priority.

Phase 3: Practice Exam Phase (5/15–5/20)

Killer.sh attempt 1: 30-something points (ran out of time)
Killer.sh attempt 2: 17 points

The scores were low, but Killer.sh is intentionally harder than the real exam — the goal here was to identify weak spots.

Phase 4: First Exam Attempt (5/26)

Result: 50 points — failed

Domains flagged as weak:

Supply Chain Security
System Hardening
Cluster Setup

Phase 5: Re-exam Prep (5/28–6/3)

Thoroughly analyzed where I got stuck in the first attempt and ran through all Killercoda scenarios again.

Phase 6: Second Attempt (6/4)

Passed!

Study Hours

Life with a dog keeps me busy, so I managed about 0–1 hours on weekdays and 1–3 hours on weekends. Since Golden Week fell during this period, I probably clocked around 10 hours over those few days.

Prerequisites

You must already hold the CKA to sit the CKS exam.

What I Did First

Learning from Those Who Came Before

I started by reading other people's exam write-ups to benefit from their experience.

Asami's article in particular was extremely clear — I came back to it many times.

Asking AI to Accompany Me

After reading those articles and forming a rough picture of my study path, I asked AI: "I want to pass CKS in one month — please be my study companion."

It then put together a study plan, and I followed it throughout.

Study Methods

I worked through the following in order.

KodeKloud CKS Course

https://learn.kodekloud.com/courses/certified-kubernetes-security-specialist-cks

Requires a paid KodeKloud plan, but you can watch topic videos and do hands-on practice side by side. The standard plan runs $35/month (roughly ¥6,000), which is enough to make you feel like you absolutely have to pass within the month. (Looking just now, the standard plan is apparently $29 — a price cut!?)

Some content is a bit dated, so double-check the official exam requirements before your attempt.

I got through about 80% of KodeKloud before running low on time, so I switched to the Killercoda-focused approach described below. (I also consulted AI on when to make that switch.)

I ended up not passing within the one-month window, but I felt confident enough that "cycling through Killercoda is sufficient" to cancel the subscription. I was pleasantly surprised that KodeKloud sends a friendly "your month is almost up!" reminder notification.

Killercoda

https://killercoda.com/killer-shell-cks

A free hands-on environment. After getting through the KodeKloud input phase, I moved here for hands-on practice. KodeKloud walks you step-by-step toward the answer, so Killercoda is closer to the actual exam format.

Killer.sh

The official practice exam bundled with the CKS purchase. I didn't use the practice exam when I took the CKA and regretted it, so this time I planned my schedule to include proper review time before sitting it.

Quick AI Quizzes in Spare Moments

Video watching and hands-on practice are heavy study methods. For tired moments or short waits during commutes, I'd ask AI to "give me a quiz" so I could keep studying in small windows.

One funny thing: the first answer choice was always the correct one 😂 (I caught on eventually and asked it to randomize the order.)

Sometimes I'd request multiple-choice questions; other times I'd ask for free-response prompts to check my command recall.

Studying After Failing the First Time

I only got 50 points on my first attempt — devastating! The result breakdown tells you which domains you struggled with, so I focused on those weak areas and just hammered Killercoda.

It paid off: I passed the second attempt with 80 points!!!!

Final Thoughts

It was rough! There were plenty of days I couldn't carve out study time, and the stress was through the roof. So relieved to be free of it now!

I learned a lot — there were things I didn't know at all, and things I'd only half-understood that I finally got a solid grasp on.

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