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Emmanuel Cousin

Senior Software Engineer
Technical Lead & Mentor
Ruby on Rails, React, TypeScript
I make teams ship better software.

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Open Source

I build tools that solve real problems. Here are some of my open source projects and contributions.

Ruby Gems

Ruby

Use jsonapi-serializer with Grape. Provides formatters and a model parser for automatic Swagger response documentation via grape-swagger.

GitHub RubyGems
Ruby

Store and access deeply nested data structures within ActiveRecord columns. Generates accessors for every level of nested hashes with automatic typecasting. 

deep_store :settings, {
  notifications: { push: true, email: true }
}
user.push_notifications_settings # => true
GitHub RubyGems
Ruby

Object-level caching for ActiveModel. Cache strings, integers, decimals, datetimes, lists, and JSON directly on your models with a simple DSL. 

class User
  include ActiveModel::Caching
  cache_string :session_token
  cache_integer :view_count
end
GitHub RubyGems
Ruby

A fluent Ruby DSL for building InfluxDB Flux queries. Chainable API for constructing queries with measurements, fields, tags, aggregations, and more. 

InfluxDB2::QueryBuilder.new(bucket: 'sensors')
  .measurement('device_metrics')
  .fields('cpu', 'memory')
  .range(start: 24.hours.ago)
  .aggregate_window(every: '5m', fn: 'mean')
  .to_flux
View PR
Ruby

A Ruby client for the ProvetCloud API, used by veterinary practices for practice management.

GitHub RubyGems

Applications

Parkour Paris (pkp)

Live application

Rails Hotwire

Back-office platform for Parkour Paris, enabling members to register for parkour classes across Paris. Full-featured scheduling, payments, and member management.

Live Site GitHub

ActivityPub Engine

Rails Engine

Rails

A Rails engine implementing the ActivityPub protocol for federated social networking. Enables Rails apps to join the Fediverse with customizable authentication and actor management.

GitHub

Contributions

Gumroad

73 merged PRs

Rails React

Major contributor to Gumroad's open-source codebase. Led the frontend migration from ERB/React on Rails to Inertia.js/React, migrated the admin panel, and shipped features including Black Friday 2025 and subscription lifecycle improvements.

Notable PRs Click to expand
View all PRs