English/英語
Japanese/日本語

Jamel Eddine Lassoued

Full Stack Engineer. Currently working in Tokyo.

Tokyo, Japan

LinkedIn
Jamel Eddine Lassoued

About

A Full Stack Engineer with 3+ years of experience building and maintaining backend services and web applications, currently working on production reliability and infrastructure modernization for Rakuten Travel, Japan's #1 online travel agency and part of Rakuten Group, one of Japan's largest technology companies.

Work Experience

Rakuten Group Inc.

On-site
Java
Spring Boot
Golang
Python
Ruby
TypeScript
React.js
Kubernetes
Jenkins
Oracle
MongoDB
Elasticsearch
2025/4 - Present

Application Engineer

  • Led Spring Boot upgrades to 3.x across multiple legacy production services, resolving breaking dependency changes, migrating deprecated APIs, improving test coverage to >85% from 10%, and conducting performance tests
  • Spearheading the migration of 1,600+ cron jobs from bare-metal VMs to Kubernetes using Apache Airflow + KubernetesPodOperator, coordinating across several service teams; built a multi-cluster POC with custom logging, error propagation, and a CI/CD DAG generation pipeline
  • Proactively identified and resolved production performance bottlenecks across high-traffic services through Jennifer APM profiling and SQL analysis; implemented OpenTelemetry and performance testing tooling across several applications
  • Built an MCP server giving the team live access to Jennifer APM across 51 production servers, reducing incident investigation time from hours to minutes
  • Driving containerization and Cloud (Kubernetes) migrations for 100+ legacy Spring Boot services; built Claude Code AI skills and a custom code search plugin bridging Bitbucket, Confluence, and Jira to automate dependency investigation, scaled to 30+ users across multiple teams
  • Developed internal React.js tooling that integrates Bitbucket, Confluence, and Jira to automate frontend bug investigation and documentation workflows

Sigma-i Co., Ltd

Remote
Python
Ruby
Flask
React.js
MySQL
Redis
2023/5 - 2025/3

Backend Developer

  • Built and maintained the backend of one of the company's main products — a web application for data entry, retrieval, and report generation
  • Worked as part of a startup team from early stage

Yumemi Inc.

Remote
Golang
DDD
Echo
PostgreSQL
2024/2 - 2024/3

Backend Developer

  • Developed an API for a personal ordering system applying Domain-Driven Design (DDD) principles

MobileCreate

Remote
Typescript
React.js
Next.js
PostgreSQL
2023/11 - 2024/3

Full Stack Developer

  • Developed a web application with route search functionality using real-time bus location data (GTFS-RT) and notification features via LINE
  • Primarily responsible for backend and infrastructure throughout the 4-month internship

Education

Oita University

2023 - 2025
Bachelor's Degree in Computer Science and Intelligent Systems

National Institute of Technology, Sasebo College

2020 - 2023
Associate's Degree in Control systems engineering

Skills

Java
Python
Golang
TypeScript
Node.js
Spring Boot
React/Next.js
Kubernetes
Docker
AWS S3
Oracle
PostgreSQL
MySQL
MongoDB
Elasticsearch

Projects

Marsa

Minimal self-hosted PaaS replacing Coolify; deploys Docker Compose apps to a VPS with automatic TLS, GitHub push-to-deploy, SSO via Zitadel (OIDC), and a goroutine-based async deploy worker pool

Golang
SvelteKit
SQLite
Docker
Caddy

Whats this kanji?

Japanese text processing and kanji lookup with offline KANJIDIC2 dictionary

Kotlin
Android