Hallen Jin

Delivered web applications and Telegram-based games for blockchain products using React and Node.js, supporting thousands of active community users. Built and maintained end-to-end frontend, backend, and database services, improving feature delivery speed by ~30% through reusable components and shared APIs. Integrated AI-powered features using OpenAI APIs to reduce manual moderation effort by ~25%.

Delivered scalable web applications using React, Next.js, Node.js, and PostgreSQL as part of a fully remote, cross time-zone team. Designed and implemented AI-assisted features using OpenAI APIs and LangChain, automating internal workflows and saving ~15–20 hours per week for operations teams. Built and maintained cloud-native services on AWS, including background jobs and API services, supporting steady user growth. Improved system reliability by introducing caching and structured logging, reducing recurring support issues by ~30%.

Owned end-to-end development of core application modules using React, Node.js, TypeScript, and MongoDB, improving feature delivery predictability. Designed and deployed services on AWS (EC2, S3, RDS) using Docker, increasing deployment reliability and environment consistency. Introduced CI/CD workflows that reduced manual deployment effort and shortened release cycles by ~40%. Improved backend performance through query optimization and API refactoring, decreasing response times by ~25%. Reviewed pull requests and mentored junior engineers, improving overall code quality and reducing onboarding time.