Kengo Hamasaki
Software Engineer
San Francisco

Kengo is an end to end web engineer from Japan. He codes for both client side and server side, and looks over infrastructure as DevOps. He is also a payment freak with an expertise in credit card payment processing. Currently have H-1B visa for working in USA.
Indiegogo, Inc.
2017-04-01 - Ongoing
Senior Software Engineer
  • Build the server-side-rendering logic for the front-end framework which is non-native for SSR and caching system to improve the performance of website with Node.js, AngularJS and Fastly.
  • Run evaluation of the modern frontend technologies from Angular, Elm, React and Vue for Indiegogo's engineering team. Additionally, look around building systems such as Rollup, Webpack, and Parcel.
  • Build fundamental development environments for Vue.js, with TypeScript, Vuex, vue-class-component, ESLint, Webpack.
  • Create Indiegogo's design system with building reusable components with Vue. Moreover document their specifications and building guidelines, design principles to share with the entire product team by Storybook.
Indiegogo, Inc.
2016-08-22 - 2017-03-31
Software Engineer
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.
  • Build user-facing features with Ruby, Ruby on Rails, TypeScript and AngularJS.
  • Build systems handling merchants from all over the world with Stripe Connect.
LINE Euro Americas Corp.
2015-04-01 - 2016-08-12
Software Engineer
LINE is a mobile messaging platform. LINE has acquired WebPay, Inc. in Feb 2015, which led Kengo to join this company.
  • Maintained web applications which is working with Ruby on Rails
  • Built automation tools for billing and supporting customers with Node.js
fluxflex, inc. / WebPay, Inc.
2012-11-01 - 2015-03-31
Software Engineer / VP of Product Development
WebPay is a startup that offers credit-card payment gateway with developer friendly API and SDKs. fluxflex is WebPay's previous company before pivoting.
  • Built RESTful API service from scratch with Ruby on Rails, Delayed Job, MySQL, HAML, Sass, and Bootstrap
  • Built Ruby, Android, and JavaScript SDKs
  • Built secure credit card payment form with JavaScript and design its UI/UX
  • Automated many manual operations with regard to credit-card payments: account activation, billing, and fraud resolution, disputes, and chargeback
  • Managed product development of whole services
  • Supported many customers with building their web application using WebPay
  • Kept highly security level of as credit card payment service
Cookpad, Inc.
2010-04-01 - 2012-10-31
Software Engineer / Infrastructure Engineer
  • Operated highly available and heavy traffic web infrastructure
  • Replaced the content delivery system with Varnish caching, by which improving availablity and response time remarkably
  • Built features for users who publish cooking recipes on
  • 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
Hatena Co., Ltd.
2008-04-01 - 2010-03-31
Infrastructure Engineer
  • Operated 500+ physical linux servers in data center and 1000+ virtual linux servers with Xen
  • Built RPM packager with resolving CPAN dependencies
  • Designed original chassis for server, based on Hydrodynamics
2010-08-27 - Ongoing
Organizer (2014, 2018, 2019), Staff (2015, 2016, 2017), Helper (2010, 2011, 2013)
RubyKaigi is an annual conference for Ruby programmers in Japan.
  • Setup and helped run the conference
  • File and apply for speakers and attendees visiting the conference
  • Built and operated the digital signage system with Node.js, Heroku, and Android (2014), EmberJS and Firebase (2016), Nuxt.js and Firebase (2018)
  • Manage inquiries from overseas attendees and sponsors
  • Work on making documents to apply the visa for attendees who visits Japan from overseas
Graduate School of Electro-Communications
Engineering - Master (Not obtained, graduated)
2009-04-01 - 2011-03-31
University of Electro-Communication
Engineering - Bachelor
2007-04-01 - 2009-03-31
Kitakyushu National College of Technology
Engineering - Associate Bachelor
2002-04-01 - 2007-03-31
見落とされているApple Payの本当の価値 - What ApplePay really means
Techcrunch Japan
Guest post on Apple Pay's business structure with regard to credit-card system for Japanese.

Web決済入門 - Web payments first guide for Web developers
Gijutsu-Hyohron Co., Ltd.
Featured article about Web payments. Gihyo is a magazine for Web developers in Japan. Detailed explanation of payment methods and credit-card payment systems and tutorials on how to integrate WebPay, PayPal, Apple In-App Purchase, and Google Play In-App Billing.

ウェブオペレーション - Web Operations
O'Reilly Japan, Inc.
Guest post on backend infrastructure of to the Japanese translation of Web Operations from O'Reilly Media.

Meguro-kai Prize
President of University of Electro-Communication
Excellent achiever among the graduates.
English (Working proficiency)
Working proficiency
Web/Mobile Development
  • Ruby / Ruby on Rails / Sinatra
  • RSpec / Minitest / Karma / Jest
  • TypeScript / JavaScript / ECMAScript 6 / CoffeeScript
  • Vue.js / Vuex
  • Webpack / Rollup
  • ESLint / Storybook
  • ERB / Haml / Slim / Pug (Jade)
  • Sass / Scss / LESS / PostCSS
  • HTML5 / CSS3
  • Angular
  • Node.js
  • Elm
  • RESTful API and Client
Backend Technologies
  • MySQL
  • Varnish
  • Apache HTTPD
  • Nginx
  • Amazon Web Service
  • Redis
  • MongoDB
  • Stripe (Payment)
Development Style / Culture
  • Test Driven Development
  • DevOps
  • ChatOps
  • GitHub Flow
  • Heroku / Heroku Flow
  • Continuous Integration
  • CircleCI

Zachary Scott @_zzak (Ex-Roomate, Co-Staff of RubyKaigi)
I've known Hamasaki-san for about 2 years now, his hard work on RubyKaigi and job are repeatedly visible. I always see him carrying a laptop, and when he stayed with me last year, for 2 weeks all he did was work.. and eat ramen. I'm confident that if I recommend hmsk for any job he would work his hardest no matter what it is.
Yohei Okada (Co-worker at WebPay, Inc.)
I worked closely with hmsk at WebPay and highly recommend him. I saw him lead product development, support customers, and handle account activation. He was the most critical member at our team, and without him, our company and product wouldn't have accomplished the same growth. He designs using css, writes clean code in ruby and javascript, and looks over the servers.