Freelancer profile translated to English.

Description

Hi! I'm Patrick — a Staff Software Engineer at Mercari (Japan), formerly CEO and Head of Engineering at Kawazu Sakura Software, a Japanese software development company.

Based in Fukuoka, Japan, native German speaker, with 4-5 hours of daily timezone overlap with Central Europe (Japan afternoon = European morning).

What I do:

- Full-stack development — Go, TypeScript, Next.js, React Native, Flutter

- Cloud architecture — production GCP at scale

- AI-augmented development — daily user of Claude Code, Codex, n8n in production at Mercari

Why I'm here:

I'm exploring side work alongside my role at Mercari. I'm currently learning a lot about AI tools and want to help teams adopt them effectively while building real products.

What I'm looking for:

- 10-15 hours per week (1-2 days)

- Building new products (especially AI-augmented)

- Open to advisory / architecture / tech lead roles

- Remote, async-friendly

Feel free to reach out — happy to discuss how I can help your team.

Industry field of expertise

Languages

German
Native or bilingual
English
Native or bilingual
Japanese
Fluent

Workplace preferences

Remote only

Primarily works remotely

Mercari, Inc. (Remote)
Staff Software Engineer (Tech Lead)
December 2023 - Today (2 years and 8 months)
• ● Lead international engineering team of 6 developers across India and Japan, coordinating across multiple time zones
• ● Architected and delivered enterprise chat feature Proof of Concept (PoC) using Google Contact Center AI within 3 months
• ● Collaborated with internal stakeholders (Customer Service, Design System, Security, Network) and external partners (Google) to ensure seamless integration
• ● Authored 10+ technical design documents and architectural decision records, improving maintainability and development velocity across international team
• ● Led full-stack development of production chat system serving 10K+ daily users
• ● Certified as Security Champion, implementing security best practices across Help Center platform
• ● Executed bi-weekly A/B tests to optimize user experience, achieving measurable improvements in customer self-service adoption
• ● Developed intelligent guide suggestion feature, reducing customer inquiries by 17,000/month while increasing guide engagement by 2.62%
• ● Designed scalable multi-tenant architecture serving Help Center features across multiple Mercari business units from unified codebase
• ● Leveraged AI development tools (Claude Code, Devin, n8n) to accelerate feature delivery and code quality
• ● Stack: Golang, Nexjs, Cloudflare, Terraform, Kubernetes, GCP
Terraform Google cloud Next.js Kubernetes Cloudflare
Kawazu Sakura Software K.K.
CEO and CTO
January 2021 - July 2023 (2 years and 6 months)
• ● Led cross-functional engineering organization of 7 developers (4 frontend, 3 backend) for high-volume cryptocurrency exchange platform
• ● Established performance evaluation framework and conducted quarterly reviews, improving team retention and development
• ● Collaborated with C-level executives and product leadership to align engineering roadmap with business objectives and market demands
• ● Architected fault-tolerant trading platform with 10+ microservices using Go, Nim, and Node.js, handling high-frequency transactions via Kafka message streaming
• ● Built comprehensive integration testing suite for microservices ecosystem and developed internal Kafka testing tools to ensure system reliability
• ● Increased engineering velocity by 30% through improved specifications, documentation, and performance management
• ● Built reusable UI component library and design system using Next.js and Storybook, standardizing frontend development across trading platform
• ● Designed and integrated GraphQL and gRPC APIs with Next.js frontend, ensuring type-safe communication between microservices and client applications
• ● Developed custom developer tooling and automation scripts, reducing new engineer onboarding and environment setup time by 50%
• ● Created initial product in 3 months and alpha version in a year from zero
• ● Stack: Golang, Nim, Kubernetes, Kafka, AWS, Nextjs, Ether.js
GO Next.js Kubernetes Apache Kafka Amazon Web Services
Kawazu Sakura Software K.K
CTO
January 2019 - July 2021 (2 years and 6 months)
Blast (6 month project) [ ]
● Delivered dual mobile applications (iOS/Android) in 3 months using Flutter and Firebase, enabling radio streaming and e-commerce functionality
● Optimized Firebase database schema and caching strategy to support 1000+ concurrent users without performance degradation
● Enhanced iOS Bluetooth communication library for seamless hardware integration, improving connection reliability and data transmission
● Stack: Typescript, Dart, Firebase, Objective C, C (Hardware code)

Asharq (6 month )
● Developed high-performance news publication platform using Gatsby, delivering scalable web application for major Middle Eastern media company
● Created custom editorial dashboard in Contentful CMS, streamlining content workflow and reducing article publishing time by 40%
● Architected serverless backend infrastructure using Node.js, AWS Lambda, and PostgreSQL, enabling automatic scaling for traffic spikes during breaking news
● Stack: Express, Javascript, Gatsby, Postgres
Typescript Firebase PostgreSQL Express JavaScript