Keunsik Works @givepro91
한국어 CV

ENGINEER · BACKEND → AI PRODUCTS

Keun-sik Jang

Engineer building AI products from a backend foundation

Backend is the foundation. Products are the direction.

givepro91@gmail.com South Korea GitHub LinkedIn Portfolio
Keun-sik Jang profile
01

Profile

Engineer who started in backend systems and now builds AI products. Over the past decade, I have worked across service architecture, asynchronous processing, data pipelines, infrastructure, and product delivery. I work from the question, “How far does this problem need me to go?”—from backend foundations to user-facing product, operations, and release.

NOW

Exploring my next role after Spacewalk and building personal products in the meantime. I make system boundaries explicit: where AI can act, where a person must approve, and how a change can be reversed and audited.

02

Experience

AARO

Part-time Consultant / Server, Infrastructure & Operations for an AI Architectural Design Platform

Consulting on servers and infrastructure for a team building an AI architectural design platform.

  • Building an internal tool that generates a design portal for each client.

TypeScript · Next.js

Dosi Jeongbi Ieum

Freelancer / Development & Operations of an Association Work Platform

Developing and operating a work platform used by redevelopment and reconstruction associations.

  • A web service that handles accounting ledgers, expense approvals, monthly reports, and scheduling in one place.

TypeScript · Hono · SQLite · AWS

Spacewalk, Inc.

Technical Product Lead / Backend & Product Team

Joined as a backend engineer and expanded into team leadership and technical product delivery.

  • Developed and operated the Landbook backend across authentication, payments, subscriptions, parcel services, and gateways. Reworked blocking calls and sequential notifications so one slow service would not hold up the rest of the system, and led the row-house redevelopment analysis service for deployment inside LH's internal network.
  • Led PlanNext.AI from planning through development and deployment, then expanded it into PlanNext Retail: site analysis, strategy options, 2D/3D automated design, validation, and DXF export.
  • Built the infrastructure and application flow for PlanReview, separating web intake from long-running document analysis with a queue. Kept analysis results consistent across the product and added deployment checks after a configuration mistake reached production.
  • Standardized server access, secrets management, and AI-assisted operations so agents could inspect infrastructure and documentation but needed human approval before making changes.
  • Built an internal operations console and led the move from cloud infrastructure to company-owned servers, reducing AWS costs to roughly one tenth. Also led code review, documentation, release processes, and onboarding for the backend team.

Kotlin · Spring Boot · WebFlux · Coroutines · Kafka · Redis · PostgreSQL · AWS EKS · Python · FastAPI

Peoplely, Inc.

Manager / Product & Engineering Lead

Planned, built, and operated an exhibition audio-guide platform and exhibition-linked commerce, while leading a small team.

  • Developed and maintained Qpicker, an exhibition audio-guide platform with a React Native app and admin back office. Integrated Firebase and payment services; the product reached 100K+ cumulative downloads and supported a Haribo Asia exhibition contract.
  • Planned and built the After Museum commerce platform, including REST APIs and payments, and delivered the MVP and AWS deployment within one month. Built CI/CD with Jenkins and Bitbucket and led a 3–5 person team.

Spring Boot · Java · REST API · JWT · Jenkins · MariaDB · Firebase

Taejeon Pharm Sales Co., Ltd.

Assistant Manager, Digital Strategy

Built commerce backend services and ERP integrations for a health-supplement platform.

  • Developed product, order, delivery, payment-state, and back-office features, and automated product and order synchronization between the ERP and storefront.

Java · Spring Boot · ERP Integration

Apsun Group

Web Developer / Strategic Planning

Led planning, development, operations, and deployment for brand web and mobile services, including an integrated admin system.

PassNJoy

Software Engineer

Developed and operated a travel and ticketing platform across payments, reservations, cancellations, inventory, and back-office tools.

Cheongju Gyocaro

Software Engineer / R&D Team

Developed and operated a regional online information service and internal data-management tools.

03

Personal Products

Products planned, built, released, and operated independently.

Tower & Mercenaries

Solo Product Builder · Paid iOS Game

A party-management game where players recruit mercenaries and climb a tower while watching automated battles.

  • Planned, built, released, and promoted the product alone; handled Apple Developer registration, review, pricing, and release operations.
  • Released at ₩3,300 on Aug 18, 2026. Two weeks later it reached #2 among all paid games and #1 in RPG on the Korean App Store, with a 4.0 rating across 24 reviews and no ad spend. After adding Traditional Chinese, it reached #1 among all paid games on the Taiwan App Store (Oct 7, 2026). Added deterministic combat conditions for reproducible balancing and published a free web demo.
  • Kept shipping after launch: moved the engine to Godot in 1.19.1 to cut device heat, then shipped through 1.24.1 by late Oct 2026, operated in Korean, English, Japanese, and Traditional Chinese. Patched an iOS 27 launch crash and reported the underlying scene-lifecycle fix upstream.

TypeScript · React · Godot · iOS

App Store ↗Case study ↗

Nolgot

Solo Product Builder · Parenting Map

A map app that helps parents of young children find a place they can actually visit today within 30 seconds.

  • Owned planning, development, data collection, App Store review, and release. Collected practical details that public datasets do not provide and reduced first-screen response time from 2,289–4,415ms to 18–29ms after reproducing a user report.

Next.js · TypeScript · Supabase · Capacitor · iOS · Vercel

App Store ↗

Climb Crew: Survivors · Belkar: Black Hunter

Solo Product Builder · Two Mobile Releases

Two mobile products taken from first commit through App Store review in nine and six days respectively, released on Sep 23 and Sep 28, 2026, and both on Google Play in October.

  • Put automated checks and on-device measurement in place before moving fast: roughly 320 regression assertions across three suites, so a build could ship without a manual pass.
  • Measured instead of assuming. Built the pre-change build in a separate worktree and ran it under identical conditions, which showed an apparent improvement was pre-existing difficulty rather than the fix.
  • Turned a vague user report ("enemies cleared but the stage will not advance") into a number: 12–13% of spawn points were pushed outside the playable area, which led to replacing pathfinding.
  • Reused an earlier product's setting while writing the IP boundary document before any code, separating what carries over from what must not, in both directions.

Godot · Unity · C# · Firebase · iOS · Android

App Store ↗
04

Selected Projects

PlanNext Retail · PlanNext.AI

Product Lead · Backend / Infrastructure / AI Serving

An AI retail-design product that analyzes a site, proposes store strategies, generates 2D/3D layouts, and exports drawings.

  • Separated conversational AI from structured design data so the 2D view, 3D view, and DXF export stayed aligned.
  • Turned the design API into a paid product with authentication, plans, usage history, and queued long-running jobs.

Kotlin · Spring Boot · Coroutines · Kafka · Redis · LLM Serving · AWS EKS

Product ↗Decision log ↗

PlanReview

Infrastructure & Application Lead

A service that checks architectural drawings against regulations after a user uploads a PDF.

  • Separated the web request path from long-running analysis with a queue so document processing would not slow the product down.
  • Kept the analysis engine's result consistent across every view and added automated deployment checks after a production configuration failure.

TypeScript · Hono · Prisma · Redis · Next.js · Python · Docker

Decision log ↗

Landbook · Row-house Redevelopment

Backend Engineer

A PropTech platform that analyzes buildable area and project profitability from land and regulatory data.

  • Joined an existing service-oriented backend and improved non-blocking communication and parallel notification delivery.
  • Led the row-house redevelopment analysis backend and adapted it for secure deployment inside a public-agency network.

Kotlin · Spring Boot · WebFlux · Coroutines · Ruby on Rails · PostgreSQL · PostGIS

Product ↗Decision log ↗

Nova

Solo Builder · Open Source

A Claude Code plugin that separates code generation from independent evaluation before changes are committed.

  • Made review a required path rather than a recommendation, using separate roles and hooks so unreviewed code cannot be committed.

Claude Code Plugin · MCP · TypeScript · Bash

GitHub ↗Decision log ↗

Ground Control

Solo Builder · Infrastructure Agent

An infrastructure agent that narrows down causes of incidents and asks the owner before taking action.

  • Designed a workflow that keeps the final decision with a human and reports confidence as clear, suspected, or hypothetical rather than unsupported percentages.

Python · FastAPI · Claude Code CLI · Slack Bolt · AWS

Decision log ↗

Realty Data Pipeline

Backend Contributor · Data Reliability

A monthly nationwide real-estate data pipeline designed to recover cleanly from blocks, errors, and interruptions.

  • Added backoff, circuit-breaking, and administrative-district checkpoints so collection could slow down safely and resume from the interrupted point.

Python · PostgreSQL · requests · Slack

Decision log ↗