TECH-ENG-28. Full Stack Lead（Core API Team）_TokyoDev

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. ◼︎ Key Responsibilities As a Full-Stack Engineer, you will play a central role within the Mico Engage AI development team. Your responsibilities include: * 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. ◼︎ 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

* 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

* 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

* Able to move forward in situations of ambiguity or undefined requirements with curiosity and initiative * Able to make technical decisions by balancing short-term effort with long-term value * Capable of rapid hypothesis testing and learning from failures * Able to set high standards through code and reviews, and inspire the team * Able to identify product issues and drive them to completion * Able to collaborate with multinational team members and openly share knowledge