James Koo

Architected and deployed agentic billing workflows using OpenAI API and Node.js, automating complex financial decision
trees and reducing manual billing effort by 45%
Designed and optimized PostgreSQL schemas for high-volume transactional systems, improving query performance by
38% under peak load
Built scalable backend services with TypeScript and Express.js, supporting millions of API requests per month with
99.99% uptime
Developed React-based operational dashboards enabling real-time billing insights, increasing team productivity by 30%
Engineered resilient third-party integrations with inconsistent financial APIs, implementing retry logic and circuit breakers
that reduced failure rates by 50%
Led implementation of structured LLM outputs and prompt pipelines, improving model accuracy in production workflows
by 25%
Deployed cloud-native infrastructure on AWS using ECS, Lambda, and RDS, reducing infrastructure costs by 20% through
optimization
Collaborated directly with domain experts to translate business requirements into scalable technical solutions, shortening
feedback cycles by 35%
Established code quality standards and led peer code reviews, reducing post-release defects by 28%
Built observability pipelines using CloudWatch and logging frameworks, decreasing incident response time by 40%

Built end-to-end SaaS platforms using React, Node.js, and PostgreSQL, delivering scalable applications with over 100K
active users
Implemented LLM-powered automation tools using OpenAI and LangChain, reducing manual processing time in CRM
workflows by 50%
Designed and maintained RESTful APIs handling high concurrency workloads, improving response times by 35%
Developed complex React interfaces for operational users, improving UX efficiency and reducing onboarding time by 25%
Integrated third-party services including payment gateways and healthcare systems, ensuring 99.9% data synchronization
accuracy
Refactored legacy monolithic systems into microservices architecture, improving scalability and deployment speed by 40%
Optimized database queries and indexing strategies in PostgreSQL, reducing latency for critical endpoints by 45%
Implemented CI/CD pipelines using Docker and AWS, decreasing deployment time by 60%
• Built secure authentication
and authorization systems, improving system security posture and compliance readiness
Partnered with stakeholders to define product requirements and translate them into technical deliverables, increasing
feature adoption by 20%

Developed full-stack applications using React and Node.js for fintech and healthcare clients, supporting high-reliability use
cases
Engineered scalable backend systems with Express.js and PostgreSQL, improving system throughput by 30%
Built interactive frontend interfaces with React and Redux, increasing user engagement by 25%
Integrated third-party APIs including financial services and analytics platforms, ensuring consistent and reliable data
exchange
Designed and implemented database schemas for transactional systems, improving data integrity and consistency
Implemented caching and performance optimizations, reducing API response times by 40%
Collaborated with cross-functional teams to deliver features aligned with business goals and user needs
Wrote comprehensive unit and integration tests, increasing code coverage to 85%
Improved logging and monitoring systems, reducing production incidents by 20%
Participated in code reviews and knowledge sharing sessions, improving team engineering standards

Developed responsive web applications using React, JavaScript, HTML5, and CSS3, improving user engagement by 30%
Collaborated with backend teams to integrate REST APIs, ensuring seamless data flow across systems
Optimized frontend performance, reducing page load times by 35%
Built reusable UI components, reducing development time for new features by 25%
Worked on e-commerce platforms, improving conversion rates through UX enhancements by 15%
Implemented state management solutions using Redux, improving application scalability
Ensured cross-browser compatibility and mobile responsiveness across all projects
Assisted in migrating legacy systems to modern JavaScript frameworks, improving maintainability
Conducted UI testing and debugging, reducing frontend bugs by 20%
Collaborated with designers and product managers to deliver high-quality user experiences