About Me
About Me
10+
Years Experience
8+
Projects
4+
Languages
With C#/.NET, Java, and TypeScript (Next.js) as my core stack, I've spent about 10 years in system development. I thrive on going beyond my assigned scope to maximize the team's overall output.
Full-Stack Development
From requirements and design to frontend/backend implementation and AWS infrastructure. I've led challenging projects to release as a PL.
AI-Driven Development
Focused on development with LLMs (Large Language Models) such as Claude Code and Codex. Actively improving development efficiency through AI assistance and proposing adoption of new technologies.
Team Building
Pair programming, code reviews, and strength-based task allocation — creating an environment where everyone can perform at their best.
What I Deliver
Hit the Ground Running
Proficient in multiple stacks — C#, Java, TypeScript. Quick to ramp up on existing codebases and deliver from day one.
End-to-End Ownership
From requirements and design to implementation and infrastructure — I handle the full lifecycle. Minimal direction needed.
Project Turnaround
Quickly identify code quality and design issues, then execute fixes. Proven track record of rescuing delayed and leaderless projects.
Technology & Innovation
AI-driven development with LLMs, modern tech adoption — I actively propose solutions that boost development efficiency.
Skills
Skills & Expertise
Languages
4Frameworks
7Databases
5Infrastructure
11Business Domains
4Career
Career History
Freelance
Cloud Accounting Service for Enterprises
April 2024 – Present|1 year 10 months
Role
Tech Stack
Details
- Full-scratch development of a cloud accounting service using microservices architecture
- Cross-functional contribution across FE/BE/infrastructure as a contract engineer
- Designed and developed features for closing, fixed assets, journals and balances, and external accounting tool integrations
- Designed and implemented backend foundations: external communications, middleware, DB access layer, and xUnit core utilities
- Architected project structure following Clean Architecture based on SOLID and DRY principles
- Built CI/CD pipeline using AWS CodePipeline
- Automated DB backup using Lambda + Step Functions
Achievements
- ▶Early delivery of BE foundations (external comms, middleware, DB access, test infrastructure) to streamline team development
- ▶Expanded coverage across FE/BE/infrastructure, eliminating team bottlenecks
All-in-One ERP Package for Apparel Industry
November 2023 – March 2024|5 months
Role
Tech Stack
Details
- Customization development of an all-in-one ERP system for apparel (sales, inventory, procurement management)
- Focused on inter-store inventory adjustment feature, from detailed design through unit testing
- Created Factory Pattern for CSV/JSON Export/Import processing, standardizing workflow, validation, and output logic
Achievements
- ▶Developed a reusable Export/Import Factory and deployed it across the team, significantly improving development efficiency
- ▶Completed assigned tasks ahead of schedule, enabling additional support for other team members
E-Commerce Management System (Full Scratch)
April 2021 – November 2023|2 years 8 months
Role
Tech Stack
Details
- Full-scratch development of a package covering order, inventory, customer, shipping, and billing management
- Dual architecture: Web app (Java — master, inventory, shipping) and Desktop app (C# — orders, customers, billing)
- Designed API integrations with Amazon, Rakuten, and Yahoo for automated order/customer data import (built as an independent ASP.NET service)
- Led system design (screen/API design) for inventory management, EC integrations, and master data features
- End-to-end ownership for custom features: requirements, acceptance testing, client training, and maintenance
- Design lead for standard package; project leader for multiple client-specific customization deliveries
Achievements
- ▶Recovered manufacturing delays by handling both design and implementation in parallel during waterfall development
- ▶Covered all phases from requirements to maintenance, driving overall project delivery
Full-Time Employment
Ticket Consignment Billing & Settlement System
July 2020 – March 2021|9 months
Role
Tech Stack
Details
- Development of a billing and settlement management system for ticket sales companies
- Designed and implemented core journal entry generation logic from transaction data
- Optimized numerous batch processes through execution-plan-aware query design
Achievements
- ▶Accurately implemented complex journal entry logic, delivering a high-quality system
- ▶Optimized batch processing performance through execution-plan-based SQL tuning
Bond Record Management System Replacement
March 2019 – June 2020|1 year 4 months
Role
Tech Stack
Details
- Replacement development of a bond record management system
- Took over full project management after PL departure: progress tracking, client negotiations, and team coordination
- Designed and implemented VBA-based report generation tool
Achievements
- ▶After PL departure, took over project management (progress, client relations, team management) and delivered to release
- ▶Reduced batch processing time from 1 hour to 15 minutes through proper index design and SQL tuning
Trust Bank Bond Trading System Replacement
July 2016 – February 2019|2 years 8 months
Role
Tech Stack
Details
- Replacement of a bond trading system for one of Japan's only 3 asset management trust banks
- Promoted from spot testing role to settlement team leader by proactively absorbing domain knowledge
- Owned core logic for settlement, reports, repo trading (collateral, mark-to-market, margin call calculations)
- Managed a 10-member settlement team: progress tracking and task assignment
- COBOL core functions executed via JP1 job scheduling (equivalent to AWS Step Functions/Lambda)
Achievements
- ▶Earned client trust by mastering core function specifications beyond anyone else, leading to team leader promotion
- ▶Led 10-member settlement team to successful delivery of all assigned releases
Major Bank Core System Maintenance
July 2015 – June 2017|2 years
Role
Tech Stack
Details
- Maintained and enhanced branch terminals, ATMs, and web services; supported system integration with another bank
- Delivered quality-first implementation and testing for mission-critical systems with zero tolerance for defects
Achievements
- ▶Completed development under strict zero-defect quality standards, building a strong foundation for quality-conscious engineering
Pension System Modification (Year 2025 Japanese Calendar Issue)
May 2014 – June 2015|1 year 2 months
Role
Tech Stack
Details
- Modified internal date handling to expand Japanese era year fields from 2-digit to 3-digit format (Showa 100 year problem)
- Developed and tested date processing logic modifications in COBOL
Achievements
- ▶Gained foundational development skills by contributing to a large-scale pension system in first year of career
Personal Works
Personal Projects
SaaS Resitoly
AI-powered expense management SaaS that auto-analyzes receipts via OCR + LLM
Blog
Blog
Coming Soon — Technical articles in progress
Contact
Contact
Feel free to reach out. I'm open to project consultations and work opportunities.
Send an Email
s_nakagawa@taluslab.com