Taishi Hasegawa
Senior Software Engineer
10+ years building scalable web applications, AI-powered products, and enterprise software. React/Next.js + Node.js/Python, production LLM & RAG systems, and distributed infrastructure.
About
Taishi
I build scalable web applications, AI-powered products, and enterprise software where performance, reliability, and real business outcomes all have to work together.
I'm a software engineer with over 10 years of experience designing and building scalable web applications, AI-powered products, and enterprise-grade software. I combine deep React, Next.js, and TypeScript expertise with hands-on LLM, RAG, and intelligent automation work, plus experience designing distributed systems and blockchain infrastructure. I focus on turning complex requirements into measurable results and lead projects through their entire lifecycle, from architectural design to deployment.
Architected and shipped an AI scheduling assistant that automated manual clinic scheduling, combining LLM-based intent extraction with deterministic constraints across multiple healthcare organizations.
Built and deployed a production-grade RAG system (document ingestion, semantic search, and answer grounding) for enterprise healthcare data.
Cut first-page load times by 85% (1.4s → 0.2s), directly improving user retention and conversion.
Built a private Hyperledger Fabric network that reduced security risks, and promoted 5 engineers from Junior to Senior through mentoring.
Professional
Experience
Over 10+ years I've grown from building responsive React applications and backend services into leading teams that ship production AI systems. My work spans LLM-powered healthcare automation, enterprise RAG, high-performance frontends, and distributed and blockchain infrastructure—owned end to end, from architecture to deployment.
And a new adventure ahead
Backend Developer
Lychee G.K. · Tokyo, JapanExperienceMar 2016 - Jul 2020- Developed a real estate platform serving 3,600 users with dynamic search and a responsive UI.
- Improved web performance by 75% through frontend optimization and efficient architecture design.
- Built responsive web applications using React, modern JavaScript frameworks, and component-based architecture.
Senior Software Engineer
OBIC Co., Ltd · Tokyo, Japan (Remote)ExperienceJan 2020 - Mar 2023- Cut first-page load times by 85% (1.4s → 0.2s), directly improving user retention and conversion.
- Shipped 5 high-impact projects to production while managing 3 cross-functional remote teams across global time zones.
- Promoted 5 engineers from Junior to Senior by mentoring them and establishing a high-performance engineering culture.
Senior Software Engineer, AI Engineer
Nekologic · Kyoto, JapanExperienceApr 2023 - May 2026- Architected and shipped an AI scheduling assistant that automated manual clinic scheduling, deployed across multiple healthcare organizations.
- Combined LLM-based intent extraction with complex deterministic constraints to automate clinic scheduling end to end.
- Built and deployed a production-grade RAG system with document ingestion, semantic search, and answer grounding for enterprise healthcare data.
- Accelerated delivery by integrating AI coding agents and LLM-based PR automation into the CI pipeline.
- Led a team of 4 engineers and owned the technical roadmap and engineering standards from initial pilot to multi-organization deployment.
M.S. in Computer Science & Engineering
Nagoya UniversityEducationApr 2012 - Oct 2016- Master of Science in Computer Science & Engineering.
- Bachelor of Computer Science.
And a new adventure ahead
Featured Work
AI products • LLM & RAG systems • Scalable web apps • Backend platforms • AI agents
AI Clinic Scheduling Assistant
Architected and shipped an AI scheduling assistant at Nekologic that automates manual clinic scheduling. An LLM extracts intent and details from free-text requests, while a deterministic constraint layer enforces every scheduling rule, so results stay valid. Deployed across multiple healthcare organizations.
Enterprise Healthcare RAG
Built and deployed a production-grade retrieval-augmented generation system for enterprise healthcare data at Nekologic. It covers document ingestion, semantic search over embedded content, and answer grounding, so responses come from the organization's own documents rather than the model's general knowledge.
AI Coding Agents & PR Automation
Integrated AI coding agents and LLM-based PR automation into the team's CI pipeline at Nekologic. Changes are drafted with agent assistance and every pull request gets automated LLM review alongside the existing build and test checks, while engineers keep the final approval.
CodeNex: AI Builder
Built a full-stack AI builder inspired by Lovable and v0, with a Java microservices backend, authentication, dashboards, usage views, and a guided builder workflow across Redis, Kafka, Docker, and Kubernetes.
CodeNex AI API Proxy
Built a provider-agnostic AI gateway that handles protocol translation, provider pooling, health-aware failover, streaming, and operational controls behind a single API surface.
Serenify
Built an open-source AI wellness platform that combines empathetic chat, mood tracking, journaling, guided sessions, and privacy-aware analytics into a product users can return to consistently.
Resume Fit — CodeNex
Built an AI resume analysis and optimization tool with ATS-style scoring, keyword extraction, guided refinements, and visual feedback for iterative resume improvement.
CodeNex Images
Built an AI image generation and editing product around Gemini models, Auth0, and a polished workspace that emphasizes creation flow instead of exposing raw model controls.
LLaMa MCP Streamlit
Built an interactive assistant that combines NVIDIA NIM-hosted LLaMA 3.3 70B with MCP to show how LLM interfaces can move beyond chat into real-time tool execution.
Technical
Stack
The technologies I reach for most often when building backend systems, full-stack products, production AI infrastructure, and LLM-powered workflows.
AI / LLM
27 technologies
The models, agent frameworks, retrieval, and inference tooling I use to build production AI products and automation.
Backend
14 technologies
The languages, protocols, and patterns I use to design reliable APIs, multi-tenant SaaS, and business logic orchestration.
Frontend & Full-Stack
11 technologies
The frameworks and data tooling I use to ship fast, responsive product experiences end to end.
Databases
7 technologies
The relational, document, search, and vector stores I use for transactional data and AI retrieval.
Cloud & DevOps
19 technologies
The cloud platforms, infrastructure, and delivery tooling I use to deploy, observe, and debug production systems.
Leadership
5 technologies
How I lead teams and own delivery beyond writing code.
Talk to my
AI Twin
Want the fast version? My AI twin can summarize my fit for a role, walk through my AI scheduling and RAG work, or explain how I think about scalable web apps, AI agents, and engineering leadership.
Best for recruiter summaries, architecture deep-dives, backend discussions, and guided project walkthroughs.
Get in Touch
Open to backend, full-stack, platform, and AI product engineering opportunities, as well as thoughtful collaborations.
Let's Build Something
If you're hiring for senior software engineering, AI/LLM products, backend platforms, or technical leadership work, I'd love to talk. I'm also open to thoughtful collaborations and open-source conversations.
