Ruby on Rails development and upgrades, from people who work on Ruby itself
We are a development company specializing in Ruby on Rails and Phoenix/Elixir. From new development to improving existing systems and technical consulting, we support your business with technology.
What We Do
From technology selection to development and operations, we support every phase of your project.
Rails and Ruby upgrades
Move an old Rails application to current Rails and Ruby step by step, without a rewrite and without stopping feature work. We start with a fixed-price roadmap.
Upgrade roadmap: $1,500
Ruby on Rails development
Ruby on Rails development at a fixed price: a first version of a new application, one feature, a fix, or monthly maintenance.
Feature or fix: from $1,000
Code audit and second opinion
An outside review of your Rails codebase, or of a proposal you have been given, written up in plain language so you can decide what to do next.
Second opinion: $500
Our Products
As proof of our technical ability, we develop and operate our own products.
Japan Voyage
A platform for finding golf, ski and travel companions in Japan, plus rental homes for people moving here. Built with Rails 8, it implements real-time notifications, multilingual support, and map search.
japanvoyage.jp
From our blog
Notes on Ruby on Rails, Hotwire, and building web applications.
Security updates for Ruby and Rails: which versions are still patched, and a routine that keeps you on them
Rails 8.0 stopped getting security fixes on 7 November 2026 and Ruby 3.2 in April. Which Ruby and Rails versions are still patched, where the announcements come from, and the weekly routine we use to apply security releases without drama.
Moving Japan Voyage to JRuby, part 1: the fiber scheduler under Falcon
Japan Voyage runs on Falcon, which runs on Ruby's fiber scheduler. Before the app can boot on JRuby, that scheduler has to behave the way CRuby's does. This is what has been fixed in JRuby so far, and what is still in the way.
RubyとRailsのセキュリティアップデート：まだ修正が届くバージョンと、取り残されないための運用
Rails 8.0は2026年11月7日、Ruby 3.2は4月にセキュリティ修正の提供が終わりました。今セキュリティ修正が届くRubyとRailsのバージョン、告知の出どころ、そしてセキュリティリリースを無理なく当て続けるための毎週の運用をまとめます。
Ruby in your browser
Interactive pages about how Ruby works inside. Each one runs real Ruby in your browser with WebAssembly.
Fiber
Fiber Lifecycle Game
Guess which line runs next as fibers yield, resume, transfer and get killed. Seven levels, checked by real Ruby.
String#tr
SWAR String#tr
Step through JRuby's fast path for String#tr, which finds and replaces eight bytes per step.
Merged in JRuby: jruby/jruby#10000
Company Profile
- Company Name
- Sampo Development LLC
- Founded
- 2021
- Location
- Suita, Osaka, Japan
- Representative
- Kuokkanen Sampo
- Employees
- 2 people
- Languages
- Japanese, English, Chinese, Finnish
Strengths
- Extensive experience with real-time communication (WebSocket, ActionCable, Phoenix Channels).
- Able to develop and communicate in a multilingual environment (Japanese, English, Chinese).
- Consistent support from design through deployment and operation.
- Objective technical evaluation as a second opinion.
Team
Sampo Kuokkanen
Representative / CEO
A Ruby and Elixir developer from Finland, living in Japan. Representative of Sampo Development LLC and head of the Evil Martians GK Japan office. A JRuby ambassador who contributes to JRuby, mostly its fiber support, and active in the Japanese Ruby community.
Speaking
- Kaigi on Rails 2023
- RubyWorld Conference 2024: “Keeping it Ruby: why your product need to have Ruby SDK”
- RubyConf Taiwan 2025: “What is happening with strings in Ruby and why is it feeling chilly?”
- COSCUP 2026: “Ruby on Ruby: ruby/spec, MRI tests, JRuby, and living on the edge”
- RubyWorld Conference 2026: “From RubyWorld to Ruby PR: Fixing defined? and Giving Back”
Anssi Kuokkanen
Engineer
A Ruby on Rails engineer from Finland, living in Japan. He specializes in UX-focused web application development, handling everything from design to implementation. His motto is building products that balance usability and maintainability.
Education
- University of Helsinki, Graduate School: Master's degree
- Kobe University, Graduate School: Exchange program
Frequently Asked Questions
- What services does Sampo Development offer?
- New Ruby on Rails and Phoenix/Elixir application development, improving and scaling existing systems, code review, architecture design, security assessment, and second opinions.
- Do you work with clients outside Japan?
- Yes. We are based in Suita, Osaka, and work in English, Japanese, Chinese, and Finnish, collaborating with teams remotely worldwide.
- Which technologies do you specialize in?
- Ruby on Rails and Phoenix/Elixir, with deep experience in real-time, WebSocket-heavy systems built with Hotwire, ActionCable, and Phoenix Channels.
- Can you improve an existing application?
- Yes. We handle performance optimization, refactoring, new features, and technical consulting on the architecture and security of existing codebases.
- How much does it cost?
- We work on small, well-defined jobs at a fixed price, and each service page lists its prices. A second opinion is $500 and a Rails upgrade roadmap is $1,500.
- How do we get started?
- Send a few lines through the contact form, or email sampo@sampo.ltd. We reply within two business days to talk about your project and how we can help.
Feel Free to Get in Touch
Whether it's an upgrade, a small project, or a second opinion, tell us about it through the contact form or by email. We reply within two business days.