Zen Kulwatcharothai

# Senior Ruby on Rails Developer

@email = "zenkulwatcharothai@gmail.com" @github = "github.com/zenkulkan" @linkedin = "linkedin.com/in/zen-kulwatcharothai"
summary.md
/* Highly motivated Senior Ruby on Rails Developer with 10+ years of experience architecting and scaling web applications, e-commerce systems, and large-scale government platforms. Expertise in backend development, complex database migrations, API design, and performance tuning. Passionate about clean code, Test-Driven Development (TDD), and agile methodologies within collaborative, remote environments. */

> ./experience

oivan.rb
Jan 2021 - May 2024, Oct 2025 - Present
Role.create!(
company: "Oivan",
title: "Senior Ruby on Rails Developer",
highlights: [
  • ▹ "Collaborate across EU time zones with a distributed agile team, consistently delivering project milestones and Jira-tracked features on schedule.",
  • ▹ "Spearheaded the backend development of the ERAD microservice for Ejar, Saudi Arabia's national rental platform, streamlining error reporting and system analysis.",
  • ▹ "Led technical development for the EJAR3 project, executing complex database migrations and refactoring core Rails service objects to ensure high availability.",
  • ▹ "Proactively resolved critical performance bottlenecks and improved system responsiveness by optimizing API performance and implementing circuit breaker patterns.",
]
)
nimble.rb
Mar 2025 - Aug 2025
Role.create!(
company: "Nimble",
title: "Contract Software Engineer",
highlights: [
  • ▹ "Developed and deployed scalable web applications utilizing Ruby on Rails and modern JavaScript frameworks.",
  • ▹ "Architected multi-tenant application environments, ensuring strict data isolation, security compliance, and system integrity.",
  • ▹ "Engineered and integrated RESTful APIs to facilitate seamless data exchange between complex internal systems and third-party services.",
  • ▹ "Implemented and maintained a custom OAuth 2.0 server for secure application authentication and centralized identity management.",
]
)
data_wow.rb
Aug 2024 - Feb 2025
Role.create!(
company: "Data Wow",
title: "Staff Engineer",
highlights: [
  • ▹ "Directed a team of 4-6 engineers to enhance the DOPA-GAME.JP online trading card platform, overseeing technical strategy and code quality.",
  • ▹ "Slashed API response times by 20% through aggressive performance tuning, database query optimization, and advanced caching strategies.",
  • ▹ "Fortified application security protocols by implementing multi-factor authentication (MFA) and strengthening role-based authorization mechanisms.",
  • ▹ "Engineered a standardized Ruby on Rails application template utilizing Grape API, reducing new project setup time by 15% across the engineering department.",
]
)
iglu.rb
Jan 2021 - May 2024
Role.create!(
company: "Iglu",
title: "Contract Ruby on Rails Developer (Assigned to Oivan)",
)
softbaked_co_ltd.rb
Apr 2020 - Mar 2021
Role.create!(
company: "Softbaked Co., Ltd.",
title: "Staff Engineer & Team Lead",
highlights: [
  • ▹ "Led a team of 3-4 engineers in scaling the Page365 e-commerce platform, delivering feature enhancements that directly contributed to increased quarterly sales revenue.",
  • ▹ "Integrated mission-critical APIs with leading courier services for automated parcel tracking, significantly reducing customer service inquiry volume.",
]
)
tourkrub_com.rb
Feb 2019 - Mar 2020
Role.create!(
company: "Tourkrub.com",
title: "Full Stack Developer",
highlights: [
  • ▹ "Revamped the platform's user interface (UI) and optimized complex ElasticSearch queries, driving measurable increases in user engagement metrics.",
  • ▹ "Leveraged Ruby on Rails, GraphQL, and ElasticSearch to deliver a robust and scalable search and booking experience, handling a peak load of 10,000 concurrent users.",
]
)
appysphere.rb
Jul 2018 - Jan 2019
Role.create!(
company: "Appysphere",
title: "Full Stack Developer",
highlights: [
  • ▹ "Partnered with Sansiri to develop a comprehensive juristic office management platform and API, streamlining operations and reducing manual tasks by 20%.",
  • ▹ "Led the transition from a monolithic architecture to a microservices-based approach, decreasing deployment time by several days per release.",
  • ▹ "Implemented key features like parcel notifications, guest management, and facility booking systems.",
]
)
hellogold.rb
Mar 2018 - Jul 2018
Role.create!(
company: "HelloGold",
title: "Ruby on Rails Developer",
highlights: [
  • ▹ "Successfully localized the HelloGold service for the Thai market, contributing to a significant increase in new user sign-ups within 3 months.",
  • ▹ "Collaborated effectively with the headquarters team in Malaysia to ensure seamless integration of localized features into the main platform.",
]
)
lockstep_labs.rb
Jul 2015 - Mar 2018
Role.create!(
company: "Lockstep Labs",
title: "Full Stack Developer",
highlights: [
  • ▹ "Engineered the full-stack architecture for Blueprint Income, a digital FinTech marketplace, utilizing a ReactJS frontend and a Ruby on Rails API backend to seamlessly process complex financial business logic.",
  • ▹ "Developed multiple minimum viable products (MVPs) for U.S.-based startups using Ruby on Rails, React with TypeScript, and a test-driven development (TDD) approach, enabling them to successfully pitch their ideas and attract investors.",
]
)

> ./skills

languages_frameworks.json
{
"stack": [
"Ruby",
"Ruby on Rails",
"JavaScript (ES6+)",
"ReactJS",
"AngularJS",
"HTML5",
"CSS3"
]
}
databases_storage.json
{
"stack": [
"PostgreSQL",
"MySQL",
"Redis",
"ElasticSearch",
"Amazon RDS"
]
}
security_identity.json
{
"stack": [
"OAuth 2.0 Provider Implementation",
"JWT",
"OpenID Connect",
"MFA",
"SSO"
]
}
tools_cloud.json
{
"stack": [
"Git",
"RESTful APIs",
"GraphQL",
"AWS (EC2)",
"Docker",
"Microservices"
]
}
methodologies.json
{
"stack": [
"Agile/Scrum",
"TDD",
"CI/CD",
"Performance Tuning",
"API Design"
]
}