[New Grad] KT DS — Coding Test + Interview (Final Offer) Recap (2021 H2)

📅 Field notes on the KT DS 2021 H2 new-grad recruitment process. Result: Final offer on 2021-12-22, onboarded 2022-01-10. I came in with a master's in mechanical engineering + AI, almost no IT background, and had just been rejected by SK E&S and Samsung Electronics. So this post might be useful to someone with a similar non-CS path.

Timeline

Aptitude + Coding test (3.5h)

Platform: Programmers.

A. Aptitude test (1h)

• 50–60 items — math · language · reasoning mix.
• Doable without special prep. KT DS aptitude is moderate across the chaebol bar.

B. Coding test (1h)

• 3 problems — 2 algorithms + 1 SQL.
• Difficulty: roughly Silver 4 / Silver 1 / Easy SQL on the Baekjoon scale.

Q1 — Stock buy/sell simulation (Silver 4)

Buy after 3 consecutive rises, sell after 3 consecutive drops. Final profit = held stock value − cash spent.

Example: [5, 3, 4, 6, 7, 9, 19, 18, 17, 16, 12, 14, 15, 20, 13] → final profit 2.

Straightforward simulation, no nasty edge cases. Doable inside time budget.

Q2 — Silver-1 implementation

Details hazy. I solved it sketching a small grid simulation on paper. Pen and paper essential.

Q3 — SQL (Easy)

GROUP BY + ORDER BY. No complex joins.

GitHub solution: Algorithm/CodingTestReproduction/ktds-codingtest

Result: passed coding + aptitude.

Pre-assignment (1h, 1 slide)

Day before interview. Pick 1 of 5 topics → produce a 1-slide PPT in 1 hour.

Topics I remember: IoT · Metaverse · Optimization algorithms · Customer-tailored services, etc.

Scenarios closely mirrored actual company problems. Internet research allowed.

💡 1 hour is short. Pack it into one-line conclusion + one slide of supporting evidence.

1-day interview (2021-12-02)

Venue: Novotel Ambassador Seoul Dongdaemun.

A. Technical interview (4:1)

Self-intro (30s)

• 30 seconds means rehearse it down. Anything longer gets cut.

Pre-assignment presentation

I initially misread the core intent of the topic. The panel clarified and let me re-answer. → Felt like they were testing communication + ability to re-read the problem.

Resume-based questions

• Collaboration experience
• Tech stack — what I'd actually used hands-on
• Project details — ~3-deep follow-ups

Company knowledge

"Tell me what KT DS actually does as a business."

Didn't know much at the time. Answered "group IT outsourcing + recent in-house projects" — would have done better with more homework.

Motivation

Tied it to the company's energy-strategy services + recent R&D themes — awkward in places.

The technical interview felt like wading through mud. I left thinking I'd failed.

B. Executive interview (2:N)

Multiple candidates rotated through similar questions.

Questions I remember: - Self-intro - Thoughts on the "MZ generation" - Why we should hire you - Leadership — why would you want to be promoted

The executive round actually went better. Admitted what I didn't know, was clear about what I did.

Final result

Offer on 2021-12-22. I'd written it off after the technical interview. SK E&S and Samsung had just rejected me, so it landed extra hard.

Joined 2022-01-10. Mech engineering + AI master's = thin IT base. Didn't know what SI was, or APIs. Caught up over ~12 months of after-hours self-study (주경야독).

Takeaways — from a non-CS perspective

• Aptitude: variable across companies; KT DS is on the easier side.
• Coding: Silver 1–2 + basic SQL. You don't need Baekjoon Gold.
• Pre-assignment: One-page conclusion under time pressure. Know the trend keywords (IoT, metaverse, customer data).
• Technical interview: every resume line is a follow-up trigger. Be honest about what you actually did vs. what your team did.
• Executive interview: "I don't know" is fine. Have your values and motivation pre-rehearsed.

If you're on a similar path, take care of yourself. Non-CS background is recoverable post-offer. Good luck.

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📦 Migrated from my own Korean blog (my own writing). Original: taehyuklee.tistory.com/4