Senior Backend Engineer (Tokyo)

Job Description

At Mico, we provide “Mico Engage AI,” a high-traffic enterprise SaaS platform used by large-scale companies, and we are looking for core members to drive product growth.

In a rapidly growing startup environment, you will have the opportunity to continuously refine the product and evolve the user experience. You will proactively tackle a wide range of technical challenges, including optimizing high-traffic systems, developing new AI-driven features, and improving real-time processing infrastructure.

While working alongside tech leads to drive development, you will also be involved in technical decision-making and the standardization of development practices. You will collaborate within a multicultural, bilingual team and enhance your skills in a global development environment.

This is a highly rewarding position for those who want to go beyond development and lead the growth of both the product and the team.

 

What is Mico Engage AI

Mico Engage AI is a communication platform with one of the largest platform integration infrastructures in Japan.

• * Customer acquisition from websites
  * Personalized messaging through data utilization
  * One-to-one customer communication
  * Integration with other systems

Through these capabilities, it comprehensively solves companies’ marketing challenges and maximizes outcomes. Its strength lies in enabling end-to-end support from customer acquisition to fan engagement.

 

What You Will Gain / Why This Role is Rewarding

Experience in Scalable System Design and AI Implementation
Gain hands-on experience building products in high-traffic environments, redesigning large monoliths, and constructing event-driven architectures for next-generation scalable systems.

Collaboration Skills in a Global Development Team
Lead design and implementation across frontend and backend in a multicultural, bilingual organization, strengthening your ability to collaborate in global environments.

Hands-on Experience Driving Product Growth
Go beyond feature development by participating in technology selection, architecture decisions, and resolving technical debt, actively shaping how products are built.

Practical Design Skills in Microservices and Micro-Frontends
Work on complex re-architecture projects that modernize internal structures while maintaining user experience, gaining expertise in modular design and implementation.

Growth Opportunities in a Technology-Driven Culture
Engage in technical discussions led by engineers and contribute to design philosophies and technology choices, developing both architectural perspective and leadership.

 

Tech Stack

Backend

• TypeScript (NestJS)
• Go

 

Frontend

• TypeScript
• Chakra UI

 

Databases

• TiDB
• Aurora MySQL
• DynamoDB
• MemoryDB for Redis

 

Infrastructure / IaC

• AWS (EC2, ECS, Route53, Lambda, Kinesis Data Streams, Firehose, SQS, SES, ElastiCache, RDS, CloudWatch, IAM, Audit, API Gateway, CodeDeploy)
• Terraform, AWS CDK

 

Middleware

• Nginx, Supervisor

 

Monitoring

• NewRelic, Sentry, AWS CloudWatch

 

Data Analytics

• Google Data Studio, Google Analytics, Metabase

 

Development Environment

• Docker
• GitHub Actions
• Amplify Hosting
• CloudFront

 

Source Code Management

• GitHub

 

Communication Tools

• Google Meet, Zoom, Slack, Notion, ClickUp

 

AI Tools

• GitHub Copilot, Devin, Claude Code, Cursor, CodeRabbit, Gemini, NotebookLM, Circleback

 

About Mico

About Us

We aim to create a richer society by realizing “Lifetime Trust” through conversations between brands and consumers.

Our mid- to long-term vision is to become the most trusted brand empowerment company in Asia, and we are actively developing our business with global expansion in mind. There are many challenges to overcome in achieving this goal, and we offer an environment where you can fully leverage your experience and take ownership as a key contributor.

 

Mission

To empower every brand by building lifetime trust through humanlike technology

Mico is a company that builds lasting relationships of trust between brands and customers through human-like AI technologies. By leveraging diverse AI capabilities, we support the enhancement of brand competitiveness and business growth.

 

Vision

Asia No.1 Brand Empowerment Company

We believe in the immense potential of every brand in the world and strive to maximize that potential to contribute to society. Our purpose is to empower every brand and support the growth of all our clients.

We do not aim for marketing that only creates fleeting moments. Instead, we believe that true brand value is unlocked by fostering sustainable trust between businesses and consumers through meaningful communication.

To realize this vision, we create inspiring experiences between brands and customers through human-like technology with user-centric UI/UX.

 

Products

Mico Engage AI

A communication platform with one of the largest platform integration infrastructures in Japan, providing end-to-end solutions from customer acquisition to engagement and retention.

 

Mico Voice AI

A service that significantly enhances the quality and efficiency of customer communication through human-like AI voice automation, creating impactful customer experiences.

 

BizClo

A solution that transforms LINE into a powerful business tool for enterprises by enabling free one-to-one chat and solving handover challenges.

 

Micomii

A LINE-based membership card service for store operators, supporting customer acquisition and repeat engagement through loyalty programs and incentives.

 

Strengths of Mico AI

High-Quality, Large-Scale Data

Mico accumulates vast amounts of high-quality data, including ad clicks, browsing behavior, and user activity, enabling AI to accurately determine the right audience, content, and timing.

 

In-House Data Development

By developing and managing datasets internally, we achieve faster and more flexible AI improvements without relying on external data sources.

 

World-Class AI Team

A global team of top engineers from Japan, India, the Philippines, Taiwan, and more continuously enhances AI accuracy and innovation.

 

Why Work at Mico

Growing Market × Growing Company

• Expanding C-commerce market projected to reach ~30 trillion yen globally
• 1100% business growth over four years in the marketing SaaS domain
• Total funding of 6.3 billion yen (Series B: 3.5 billion yen)
• No.1 in LINE marketing in Japan

 

Strong Customer Focus

• Mission-driven culture focused on expanding business potential
• “WOW THE CUSTOMER” mindset to deliver impactful results

 

People and Culture

• Open and transparent communication
• Strong team collaboration (All for One)
• Giver mindset
• Global organization with members from over 20 countries

 

Work Environment

• * Flexible working style (hybrid work, flextime, 6 days of life/health leave annually)
  * Learning support (up to 55,000 yen for books and seminars)
  * High transparency (all-hands meetings, quarterly business updates)
  * Management development through structured training
  * Fair evaluation system based on OKRs with continuous feedback

 

Responsibilities

As a Senior Backend Engineer, you will play a central role in the development team for Mico Engage AI.

Stabilization of Delivery Infrastructure
Develop infrastructure that ensures stable delivery even for clients with a large user base

New Feature Development
Enhance product value by developing features aligned with the product roadmap

Customer-Driven Development
Build high-impact, reusable features based on customer needs identified through customer success activities

 

Requirements

Experience

• 5+ years of hands-on experience in system development using at least one of the following: TypeScript, Java, Go, or Python
• Experience working with multiple programming languages
• Experience in designing and developing REST APIs
• Practical experience in software design, including the application of SOLID principles and design patterns

 

Skills

• Ability to independently drive and complete the full development lifecycle, from requirements definition and specification design to implementation, testing, and release
• Ability to design scalable and maintainable system architectures that are resilient to change
• Ability to improve team-wide productivity and quality through code reviews and implementation of test code
• Business-level proficiency in Japanese communication

 

Nice to haves

Experience

• Frontend development experience using frameworks such as Next.js
• Experience developing with TypeScript
• Experience developing with Go
• Experience in API development using gRPC
• Experience in design and development based on Domain-Driven Design (DDD) and Clean Architecture
• Experience in building and operating CI/CD pipelines
• Experience in infrastructure development (e.g., AWS, Docker)
• Experience leading development as a tech lead (2+ years, managing a team of 5 or more members)

 

Skills

• Ability to make technical decisions and select appropriate technologies based on requirements, cost, and operational considerations
• Ability to leverage AI to improve development productivity and quality
• Ability to organize knowledge on effective AI utilization and share it with the team
• Business-level proficiency in English communication