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

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.

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

“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