# Kengo Hamasaki

> Product Engineer

Location: San Francisco, California, United States
Profile: https://flows.cv/kengo

Kengo is an end to end web engineer from Japan. He started his career from DevOps but shifted his primary focus toward Frontend until today through Middleware and Backend. Dove into product management, design, and customer support as a first employee of a fast-growing startup. Current favorite areas are "payment processing" and "static site generation". Loving OSS development.

## Work Experience
### Software Engineer @ Persona
Jan 2021 – Present | San Francisco, California, United States
Building product platforms, overseeing frontend infrastructure, and making subtle tools. Writing Ruby, TypeScript, and C.

-- To job seekers, please apply through Persona's website. I'm only open to chatting or making referrals if you are an authentic OSS developer.
-- To recruiters, Persona generally doesn't have a ladder or title system for engineering employees. Please keep in mind that I'm not desiring a "Senior+" title :)

### Technical Advisor @ Nstock
Jan 2024 – Present | Tokyo, Japan

### Angel Investor @ Various Startups
Jan 2016 – Present
Investing in 20+ seed-ish startups in the US (Mostly via LP) and Japan.

### Software Engineer @ Kipp Financial Technologies
Jan 2020 – Jan 2024 | Tokyo, Japan
Build internal tools; gRPC/GraphQL web clients with TypeScript and Next.js.

### Product Designer @ Kipp Financial Technologies
Jan 2018 – Jan 2020 | Tokyo, Japan
Designed whole UX of an unreleased Fintech mobile app with Flowmap and Figma.

### Senior Software Engineer II @ Indiegogo
Jan 2020 – Jan 2020 | San Francisco Bay Area
Indiegogo is the place for entrepreneurial projects to move quickly from concept to market, amplified by a community of backers who believe the world benefits when every idea gets an equal shot at success.

✔️ Main technical area was in "Ruby on Rails backend" and "Angular.js/Vue.js frontend". Worked for a ton of feature development of indiegogo.com.

✔️ As an individual contributor, keeping productivity high in building products and supporting other developers; Made the most number of commits to our main repository in 2018, the second-most in 2019. Also, reviewed the most number of Pull Requests in 2018, 2019.

✔️ Led some projects that were depending on Stripe API: Planned and ran migrations for 100k+ Stripe Connect accounts to follow new API requirements, built a new payment process with SCA aka 3D Secure, renewed a customer verification process to support new eKYC requirements, built a comprehensive UI+API to accept bank information of multiple countries/currencies.

✔️ Led replacement of frontend stack long time; Kept up-to-date of depending libraries continuously. Created Indiegogo's design system from scratch with involving designers. Initiated a whole new frontend technology stack to replace Angular.js with Vue.js.

✔️ Dove into some experimental projects to evaluate half-backed technologies. Built an original SSR system for non-SSR-ready Angular.js 1.x with Node.js express server and ESI (Edge Side Inclusion) with Varnish(Fastly). Ran evaluation for modern frontend frameworks (Elm, Angular, React, and Vue) and technologies (Build systems, template engines, ...etc).

✔️ Published some OSS through indiegogo org on GitHub: vuex-module-validatable-state, vue-sfc-analyzer-webpack-plugin.

### Senior Software Engineer @ Indiegogo
Jan 2017 – Jan 2020 | San Francisco Bay Area

### Software Engineer @ Indiegogo
Jan 2016 – Jan 2017 | San Francisco Bay Area

### Technical Advisor @ Chomp: Tasty Adventure
Jan 2017 – Jan 2017 | San Francisco Bay Area
- Built a "Continuous Delivery" pipeline of React Native based iOS app with Fastlane, Circle CI
- Initiated their testing environment with Enzyme and Jest

### Technical Advisor @ Ramen Hero
Jan 2017 – Jan 2017 | San Francisco Bay Area
Built their launching EC website application with Shopify. 

Implemented with Vue.js, ES6 (Babel), Webpack, Sass, ESLint, Karma, Chai. Served with surge.sh, Continuous Deployment with CircleCI.

The product owner had decided to switch the website to fully Shopify, so the web app is already shut down.

### Software Engineer at LINE Euro-Americas Corp. @ WebPay, Inc.
Jan 2015 – Jan 2016 | San Francisco Bay Area
ℹ️ LINE had acquired WebPay, Inc. in Feb 2015, which led Kengo to join to LINE Euro-Americas Corp.
However, his main work was almost the same as before.
https://www.crunchbase.com/organization/webpay

### VP of Product Development @ WebPay, Inc.
Jan 2014 – Jan 2015 | San Francisco Bay Area

### Founding Software Engineer @ WebPay, Inc.
Jan 2012 – Jan 2014 | Tokyo, Japan
WebPay is a startup that offers a credit card payment gateway with developer-friendly API and SDKs, which are primarily compatible with Stripe (US).

As a first employee, led the whole product development and all of the user-facing parts of the company.

✔️ Built RESTful API service which is compatible with Stripe API from scratch with Ruby on Rails, Delayed Job, MySQL, HAML, Sass, and Bootstrap

✔️ Built Ruby, Android, and JavaScript SDKs for external developers who use WebPay

✔️ Built the secure credit card payment form with JavaScript and designed its UI/UX like Stripe.js as of today

✔️ Automated many manual operations around credit-card payments: account activation, billing, fraud resolution, disputes, and chargeback

✔️ Supported many customers/developers who build their web applications using WebPay

✔️ Managed product development of whole services

✔️ Kept high-security level of webpay.jp as a credit card payment service (PCI DSS Level 1 as a service provider)

### Software Development Advisor @ WHILL, Inc.
Jan 2014 – Jan 2016 | San Carlos, California, United States
Helped WHILL's software strategy for sales/operations as an advisor and a developer.

- Built a web application to run their sales/operations with Ruby on Rails, PostgreSQL, Bootstrap
- Built development systems to review/release pipelines with GitHub, Heroku(Preview App), and Circle CI

### Android Application Developer @ Zaim Inc.
Jan 2012 – Jan 2014
Built Android client application "Zaim" with Java for switching the codebase from Titanium Mobile (JavaScript). The UI is fully following the standard of Android 4: Holo, Action bar pattern.

### Teaching Assistant @ Hitotsubashi University
Jan 2012 – Jan 2013 | Tokyo, Japan
The class of "社会科学における情報技術とコンテンツ作成III/IV" by Kuniaki Igarashi, taught programming with Ruby and web development with Ruby on Rails for bachelor/master course students.

https://github.com/igaiga/hitotsubashi-ruby-2012
https://github.com/igaiga/hitotsubashi-ruby-2013

### Software Engineer @ COOKPAD Inc.
Jan 2011 – Jan 2012 | Within 23 wards, Tokyo, Japan
Cookpad runs the biggest cooking recipe sharing service. https://cookpad.com/

✅ Built features for users who publish cooking recipes on cookpad.com
✅ Built simple framework which provides a JavaScript API for native Android interfaces
✅ Built and released two Android applications, one of which has over 5 million downloads on Google Play

### Server, Network Operations Engineer @ COOKPAD Inc.
Jan 2010 – Jan 2011 | Within 23 wards, Tokyo, Japan
✅ Operated highly available and heavy traffic web infrastructure
✅ Replaced the content delivery system with Varnish caching, by which improving availability and response time remarkably

### Infrastructure Engineer @ Hatena Co., Ltd.
Jan 2008 – Jan 2010 | Within 23 wards, Tokyo, Japan
✅ Operated 500+ physical Linux servers in the on-premise data center and 1000+ virtual Linux servers with Xen
✅ Built the internal tool to package RPM (yum) of CPAN with resolving dependencies automatically
✅ Designed original chassis for server, based on Hydrodynamics

### Teaching Assistant @ The University of Electro-Communications
Jan 2009 – Jan 2009 | Tokyo, Japan
The class of "Computer literacy". Students learn how to use UNIX(Open Solaris) and some software which run on the UNIX system like Emacs.


## Education
### Master of Engineering - MEng in Systems Engineering
The University of Electro-Communications

### Bachelor of Engineering in Systems engineering
The University of Electro-Communications

### Associate of Engineering in Control Engineering, Information Engineering, Robotics
National Institute of Technology, Kitakyushu College


## Contact & Social
- LinkedIn: https://linkedin.com/in/hmsk
- Portfolio: http://hmsk.me/
- GitHub: https://github.com/hmsk

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Source: https://flows.cv/kengo
JSON Resume: https://flows.cv/kengo/resume.json
Last updated: 2026-04-13