Position
CONCRETE CO., LTD (100% Japanese-invested) is looking for an outstanding Backend Developer to help bring the latest backend and AI technologies into real-world products.
Job Description
- Design and build scalable backend/API architecture for production products
- Optimize performance, security, and reliability at production scale
- Collaborate with the Frontend team to integrate AI-powered features (chatbots, smart recommendations, workflow automation) into the product
Requirements
Technical Skills
- At least 4 years of experience building backend systems for real production products (not just personal projects)
- Advanced proficiency in at least one backend language (PHP/Laravel, Node.js, Python…), with a solid understanding of system design principles
- Strong knowledge of databases (MySQL/PostgreSQL), RESTful/GraphQL API design, caching, message queues
- Hands-on experience integrating AI/LLM APIs (OpenAI, Claude, Gemini…) into production backend systems — function calling, streaming, async processing
- Understanding and hands-on experience with RAG (Retrieval-Augmented Generation) and vector databases (pgvector, Pinecone, Qdrant…) is a strong plus
- Experience using AI coding agents (GitHub Copilot, Claude Code, Cursor…) and agentic workflows in daily development
- Solid understanding of system security, containerization (Docker), and CI/CD
- Able to read English technical documentation; Japanese is a plus
Work Attitude & Style
- Ownership
- Transparency
- Availability
- Proactively suggests AI-driven process improvements
Working Hours
- Monday to Friday: 8:00 am – 5:00 pm
- Lunch break: 11:45 am – 12:45 pm
Benefits
- Competitive salary based on ability
- Flexible working hours and location
- Professional Agile environment
- Training and access to the latest AI tools and trends
- Work with a passionate, experienced team