Jun Sumida
Software Engineer CTO
Chiyoda, Japan
Summary
👤
Senior🎓
Top SchoolJun Sumida is a seasoned software engineer and CTO with 12 years of experience building scalable web and back-end systems across startups and large product teams in Japan. He blends hands-on expertise in React/Next/Vue, Elixir, Ruby, and TypeScript with strong infrastructure skills—CI/CD, Docker, Jenkins, AWS/GCP and automation—to lead teams from architecture to production. At mixi he led payment, MVNO and high-traffic game backend projects, managed hundreds of servers, and introduced automation and monitoring at scale while coaching agile practices. Currently steering product and engineering at S, he pairs pragmatic leadership with deep technical fluency and a taste for clean architecture and TDD. Colleagues know him as a developer who still ships code despite calling himself a “professional procrastinator,” reflecting a candid, results-oriented style.
12 years of coding experience
10 years of employment as a software developer
Bachelor of Arts, Linguistics, (Computer Science), Bachelor of Arts, Linguistics, (Computer Science) at International Christian UniversityBachelor of Arts, Commerce, Bachelor of Arts, Commerce at Waseda University
Japanese, English, French
Github Skills (23)
livekit9
ruby-on-rails6
react6
webrtc6
rails6
sdk5
ruby5
javascript5
typescript4
elixir3
phoenix-framework3
react-components3
browser3
swagger2
partitioning2
Programming languages (5)
Github contributions (5)
mixi-inc/RubyTraining
Mar 2014 - May 2014
Contributions:169 commits, 1 comment in 2 months
ruby-on-railsrailsrubytrainingruby-training
junsumida/vitess-ruby-client
Nov 2015 - Jan 2016
Contributions:62 commits, 3 PRs, 52 pushes in 2 months
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