Jaeyoung Ahn
Fullstack Software Architect
About
A technology leader who has driven architecture design, stack decisions, and code quality management at early-stage startups, delivering rapid product launches on a stable technical foundation.
Grounded in end-to-end full-cycle experience, I champion an agile development culture focused on frequent MVP releases and fast product–market fit discovery through continuous customer feedback.
Across diverse domains including logistics, healthcare, clinical research, and SaaS, I have directly experienced how technology translates into business outcomes, and I thrive in organizations where the engineering team moves in lockstep with sales and marketing to maximize impact.
Experience
2025.08 — Present
10 mo
Hwaseong, South Korea
Technical Lead
Perfectory Inc.
A solo, full-stack effort to design and build the entire technology stack for 'Gongzzang', an industrial real estate proptech platform. Single-handedly developing the whole microservices monorepo — backend, frontend, mobile, LLM, data pipeline, auth, and infrastructure — and modeling a complex real estate domain with a DDD + CQRS architecture. I personally design and implement the LLM-powered features, elevating AI into a core product value, and the platform keeps expanding fast along its roadmap (mobile app, new data layers, and more).
- Solo-architected a DDD + CQRS system — encapsulated a complex real estate domain into aggregates and separated writes (JPA) from reads (jOOQ) to optimize spatial map queries and large-scale compound reads
- Built the AI listing-description engine end to end — a LangGraph workflow analyzes listing data and streams the description, key highlights, and keywords in real time; personally designed the LLM security layer with prompt-injection defense and output masking
- Map-based composite search UI — integrated multiple layers (court auctions, actual transaction prices, industrial complexes, building deterioration) into a single map; sustained high-volume performance with an abstract-class marker system and Canvas rendering
- Public-data ETL pipeline — cleaned and loaded data from multiple government sources, refreshing it with zero downtime via atomic table swaps
- Infrastructure as code and zero-downtime delivery — managed the entire infrastructure with IaC, ran Blue/Green deployments, and built CI/CD that auto-ships only the services that changed
- Single-handedly owning the full cycle — from planning through design, development, deployment, and operations — across the user and admin web apps and the mobile app, on an active project that keeps expanding along its roadmap
2021.12 — 2025.05
3 yr 5 mo
Seongnam, South Korea
Chief Technology Officer
Sprint Inc.
Drove the full product lifecycle — from ideation and design through development, deployment, operations, and iteration — at a seed-stage startup, delivering technology-driven products capable of responding rapidly to market demands. Generated tangible business outcomes through full-stack capability spanning backend, frontend, mobile, and cloud infrastructure, underpinned by a flexible Domain-Driven Design (DDD) architecture.
- AI Diet Feedback System — Automated LLM-based feedback generation with LangChain; designed a modular prompt architecture and LangServe API server; instrumented performance logging with Langfuse
- Advanced Korean Food Search Engine — Implemented high-precision search using ngram and Jamo analyzers combined with synonym and dictionary-based matching; applied Pinned Query weight control and zero-downtime dictionary deployments
- Trainer Booking and Schedule Management System — Built an Angular + FullCalendar UI; resolved concurrent booking conflicts with Optimistic Locking; structured booking policies at the domain level
- Hybrid Billing and Payment System — Supported concurrent pay-per-use and subscription models; integrated multiple payment methods via PortOne API; automated payment workflows through domain events
- End-to-end ownership from conception to deployment; maintained service stability through CI/CD, zero-downtime deployment, and observability-driven operational practices
2021.08 — 2021.12
4 mo
Hamburg, Germany
Fullstack Java Engineer
Clariness
At a clinical trial platform company, led the DDD-based restructuring of a legacy project, maintained Next.js/Nest.js applications, and designed survey functionality for clinical studies.
- Led legacy project restructuring using DDD — separated patient, research center, and survey domains; defined Aggregates; applied Domain Events, Value Objects, and CQRS patterns
- Refactored and performance-optimized the Next.js frontend and Nest.js backend; refined API specifications
- Designed the UI/UX and data model for clinical study surveys — including skip logic, multiple response types, and data integrity guarantees
2020.03 — 2021.07
1 yr 4 mo
Hamburg, Germany
Software Engineer
Container xChange
At a container logistics platform, contributed to backend and frontend development and led the microservices architecture design for the financial module.
- Java Spring Boot Backend — Optimized data retrieval performance using DTO Projection and Native Queries; established a robust unit and integration testing framework
- Angular Frontend — Designed a reusable UI component library; implemented Redux-based state management and RxJS optimizations
- Led Financial Module Microservices Architecture Design — Applied DDD-based domain modeling, Hexagonal Architecture, Rich Domain Model, CQRS, Domain Events, and Saga Pattern
- Served as the technical communication bridge between product and engineering teams; collaborated effectively in an international, English-speaking environment
2019.02 — 2020.02
1 yr
Hamburg, Germany
Software Designer
PORTRIX LOGISTIC SOFTWARE GmbH
At a logistics software company, spearheaded the development of a next-generation Freight Management System and independently built an internal issue management tool for the support team.
- Built an FMS showcased at the 2019 Munich transport logistics trade fair — designed domain-driven process flows, Material Design UI/UX, and implemented an Angular + NestJS prototype that garnered strong interest at the exhibition
- Independently developed a dedicated issue tracking system for the support team — delivered real-time issue visibility, automated report generation via NestMailer + Mustache templates, and significantly reduced manual reporting workload
2016.10 — 2019.01
2 yr 3 mo
Hamburg, Germany
Freight Forwarding Operator
CJ Logistics
In the ocean freight division, led inland transportation optimization, ERP enhancement, and Excel VBA-based process automation — demonstrating both deep logistics domain expertise and hands-on technical capability.
- Selected as Top Performer of the Year in the company-wide annual review for 2017
- Reduced trucking costs by approximately 15% through an improved logistics vendor sourcing strategy
- Independently developed an Excel VBA-based Freight Management System, saving approximately €40,000 per year in labor costs
- Visualized inland transportation cost data with Tableau, reducing RFQ response time by approximately 70%
- Automated SAP S/4HANA invoice issuance with email integration, cutting invoice dispatch time by approximately 80%
- Developed a 3D cargo volume calculator, established a cloud document-sharing framework, and reduced inter-departmental communication overhead by approximately 50%