Fullstack Lead Engineer

Mico provides Mico Engage AI, a high-traffic enterprise SaaS used daily by major companies, and we are currently hiring core members to join our team. In our fast-growing startup environment, you will have the opportunity to directly shape the product and elevate the user experience.

You will be expected to proactively tackle a wide range of challenges—including optimizing high-traffic systems, designing and developing new AI-powered features, and improving our real-time processing infrastructure. Working closely with our Lead Engineer, you will drive product-critical development while also contributing to technical decision-making and standardization.

By collaborating in a multicultural, bilingual team, you will sharpen your skills in a global development environment. This role offers far more than pure development—you will play a key part in the growth of both the team and the product, making it a highly rewarding position.

What You Will Gain

• Experience building scalable systems and implementing AI technologies
• Collaboration skills in a global engineering team
• Hands-on experience driving product growth end-to-end

Tech Stack

• Web Backend (Mico Engage AI): TypeScript (NestJS), Go, Elixir
• Web Frontend: TypeScript (Next.js), Chakra UI
• Databases: TiDB, Aurora MySQL, DynamoDB, MemoryDB for Redis
• Infrastructure: AWS (Cognito, EC2, ECS, Route53, Lambda, Kinesis Data Stream, Kinesis Firehose, SQS, SES, ElastiCache, RDS, CloudWatch, IAM, Audit, API Gateway, CodeDeploy), IaC (Terraform, AWS CDK)
• Middleware: Nginx, Supervisor
• Monitoring: New Relic, Sentry, AWS (CloudWatch)
• Data Analytics: BigQuery, Google Data Studio, Google Analytics, Metabase, Trocco
• Environment Setup: Docker
• CI: GitHub Actions, Amplify Hosting
• CDN: CloudFront
• Source Control: GitHub
• Communication: Google Meet, Slack, Notion, Redmine, Jira, ClickUp

Responsibilities

• Stabilizing the Mico Engage AI delivery infrastructure: Build and improve the infrastructure that enables stable, large-scale delivery even for clients with high user volumes.
• Developing new features: Implement product-enhancing features based on our product roadmap.
• Customer-driven development: Build high-impact, reusable features based on needs identified through Customer Success activities.

Requirements

• 5+ years of hands-on experience in system development
• Experience developing with TypeScript and React
• Full-stack engineering experience (both frontend and backend)
• Ability to independently handle the full development cycle from requirements definition to release
• 2+ years of code review experience
• Ability to write test code and contribute to improving product quality
• Experience in technical decision-making (evaluating technical requirements, cost, and maintainability to make balanced decisions)
• 2+ years of experience leading development as a technical lead (teams of 5+ members)
• Experience designing REST APIs
• Business-level proficiency in Japanese

Nice to haves

While not specifically required, tell us if you have any of the following.

• Experience developing with Go
• Experience designing systems using Domain-Driven Design or Clean Architecture
• Experience developing gRPC APIs
• Ability to effectively leverage AI to improve development speed and quality, and to document/share best practices for AI utilization
• Experience developing with Next.js
• Experience building CI/CD pipelines
• Experience in infrastructure setup (AWS, Docker, etc.)
• Business-level proficiency in English

Compensation

¥7,000,000 ~ ¥10,000,000 annually.