Senior Fullstack Engineer (Tokyo)

Job Overview

About the Role

Mico Message is Mico’s AI-native customer engagement platform. Through messaging automation, real-time communication, and AI-powered interactions, we develop systems that build meaningful relationships between businesses and their customers.

As a Full Stack Lead Engineer, you will lead the design and development of both frontend and backend systems powering Mico Message. Beyond implementation, you will provide technical leadership across architecture design, engineering best practices, mentoring, and operational excellence.

Working closely with our Product, Design, AI, and Infrastructure teams, you will help deliver scalable and intuitive customer engagement experiences used by enterprise customers in Japan and across global markets.

 

Responsibilities

• Lead the design and development of scalable frontend and backend systems for Mico Message
• Build and enhance customer-facing applications as well as internal operational tools
• Design robust APIs, backend services, and platform integrations
• Drive technical decision-making and contribute to system architecture discussions
• Collaborate closely with Product and Design teams to shape product direction and user experience
• Continuously improve system reliability, scalability, performance, and operational observability
• Develop well-tested, maintainable code following modern engineering best practices
• Establish and improve engineering standards, development workflows, and technical processes
• Mentor engineers through code reviews, technical guidance, and knowledge sharing
• Troubleshoot and resolve complex production issues in distributed systems
• Communicate effectively across cross-functional teams in both Japanese and English
• Take end-to-end ownership from requirements gathering through production deployment and ongoing operation

 

What We Expect

We are looking for someone who can:

• Enjoy solving complex technical and product challenges while balancing speed and long-term maintainability
• Communicate effectively with both technical and non-technical stakeholders
• Work independently while collaborating in a distributed, remote-first environment
• Take meaningful ownership of system architecture and product direction
• Contribute proactively to engineering culture and technical standards

 

What You'll Gain

• The opportunity to shape the future of AI-powered customer engagement
• Significant influence over architecture, engineering standards, and product direction
• High ownership and autonomy in decision-making
• A collaborative, global, remote-first engineering culture
• Continuous learning and professional growth opportunities
• Competitive compensation and benefits
• Flexible working arrangements built on trust and accountability

 

Career Opportunities

• Advance your expertise as an Engineering Lead toward roles such as Software Architect or Technical Lead
• Grow into Engineering Manager or CTO-track positions through involvement in both product and business strategy
• Play a key role within a global engineering organization

 

About Mico

At Mico, our mission is to create a richer society by building Lifetime Trust between brands and consumers through meaningful conversations.

Our long-term vision is to become Asia's No.1 Brand Empowerment Company, delivering the most trusted customer engagement platform across Asia.

Achieving this vision requires solving ambitious technical and business challenges—and we're looking for exceptional people who are excited to tackle them.

At Mico, every team member is empowered to take initiative and make a meaningful impact.

 

Mission

To empower every brand by building lifetime trust through humanlike technology.

We believe every brand deserves the opportunity to create meaningful moments with its customers.

Through AI-powered, humanlike technology, Mico helps brands build lasting relationships that drive sustainable business growth.

 

Vision

Asia No.1 Brand Empowerment Company

We believe every brand has unlimited potential.

Our purpose is to empower every brand by helping businesses build sustainable trust with their customers—not simply through marketing campaigns, but through meaningful, human-centered communication.

With intuitive UI/UX and humanlike AI technology, we create engaging customer experiences that unlock the true value of every brand.

 

Our Products

Mico Engage AI

Japan's leading customer engagement platform with one of the country's largest messaging integration ecosystems.

The platform provides an end-to-end solution covering:

• Customer acquisition from websites
• Personalized messaging powered by customer data
• One-to-one customer communication
• Integration with external systems

Helping businesses grow from customer acquisition to long-term loyalty.

 

Mico Voice AI

An AI voice platform that automates outbound customer calls using highly natural, humanlike speech.

Beyond automation, it creates memorable customer interactions while improving both operational efficiency and customer engagement.

 

BizClo

A solution that enables enterprise companies to fully leverage LINE as a strategic business communication channel.

BizClo removes the limitations of one-to-one LINE chat, enabling organizations to build scalable and sustainable customer relationships.

 

Micomii

A LINE-based membership platform for retail stores and restaurants.

Features including digital membership cards, loyalty programs, stamp rallies, and rewards help businesses increase repeat customers without relying on third-party marketplace platforms.

 

Why Mico AI?

Massive, High-Quality Data

Mico leverages vast amounts of customer interaction data—including clicks, browsing behavior, and engagement history—to power highly accurate AI decision-making around:

• Who to engage
• What content to deliver
• When to deliver it

Our competitive advantage comes from both the quality and scale of our proprietary data.

 

Proprietary Data Infrastructure

Unlike many AI companies, we build and manage our own datasets.

This enables faster iteration, greater flexibility, and continuous AI improvement without relying on third-party data providers.

 

World-Class AI Team

Our AI organization includes talented engineers from Japan, India, the Philippines, Taiwan, and many other countries.

Together, they continuously improve the accuracy and capabilities of our AI technologies.

 

Why Join Mico?

High-Growth Market × High-Growth Company

• Serving the rapidly expanding Commerce SaaS market, expected to exceed ¥30 trillion globally
• 1,100% business growth over the past four years
• ¥6.3 billion in total funding (including ¥3.5 billion Series B)
• Market leader in LINE marketing solutions in Japan

 

Required Qualifications

• 5+ years of professional software engineering experience
• Experience working in Agile and Scrum development environments
• Business-level proficiency in both Japanese and English
• Strong full-stack web application development experience
• Experience with frontend technologies such as React, Vue.js, or Next.js
• Experience with backend technologies such as Node.js, Python, Elixir, Ruby, or PHP
• Experience designing scalable APIs and backend systems
• Deep understanding of software architecture, system design, and technical trade-offs
• Experience with relational databases such as PostgreSQL or MySQL
• Experience owning production systems in live environments
• Experience mentoring engineers and leading technical initiatives
• Excellent communication, debugging, collaboration, and problem-solving skills
• Ability to thrive in ambiguous environments and proactively drive projects forward

 

Preferred Qualifications

• Experience with statically typed languages, including TypeScript or Python type hints
• Experience using gRPC and Protocol Buffers
• Experience with Elixir/Phoenix or functional programming
• Experience building scalable SaaS platforms
• Understanding of conversational AI and LLM-powered applications
• Experience designing event-driven architectures and distributed systems
• Experience collaborating closely with Infrastructure or DevOps teams
• Experience improving engineering processes and development workflows
• Experience working in fast-growing startups
• Interest in AI-assisted software development workflows

 

Ideal Candidate

We're looking for someone who:

• Enjoys solving complex technical and product challenges
• Balances speed with long-term maintainability
• Communicates effectively with both technical and non-technical stakeholders
• Thrives in collaborative, distributed environments while working independently
• Takes strong ownership of systems and product direction
• Is passionate about shaping engineering culture and raising technical standards

 

Location

You may choose to work from either our Tokyo or Osaka office, depending on your preference.

We offer a hybrid work model, combining remote work with office attendance. Employees are encouraged to work from the office at least once per week.

 

Employment Type

Full-time

 

Working Hours

• Standard working hours: 9:00 AM – 6:00 PM
  (Includes a 1-hour lunch break)
• Flexible working hours with core hours from 10:00 AM to 4:00 PM
• Employees above a certain grade may be eligible for a discretionary work system in accordance with company policy.

 

Holidays & Paid Leave

• Saturdays, Sundays, and Japanese national holidays
• Year-end and New Year holidays
• Summer vacation
• Bereavement leave
• Annual paid leave
  • 10 days granted upon joining, with additional days based on tenure
• Other company-designated holidays

 

Probation Period

• 3 months (in principle)
• No changes to compensation or benefits during the probation period

 

Benefits

• Transportation allowance (bicycle commuting permitted)
• Company-provided laptop
• Company mobile phone (for eligible positions)
• Flexible work start time selection (can be requested every two months)
• Comprehensive social insurance
  • Health insurance
  • Employees' pension
  • Employment insurance
  • Workers' compensation insurance
• Life & Health leave
• Annual health checkups
• Parental and childcare support programs
• Employee club activities