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Senior Full-Stack Engineer with 5+ years building scalable SaaS products using Python (FastAPI/Django), React/Next.js, and PostgreSQL. Experienced in integrating AI/LLM features, including RAG pipelines, OpenAI API, and vector databases. Track record of shipping MVPs from scratch, scaling platforms from hundreds to 20,000+ users, and improving conversion/performance by measurable margins. Available 30–40 hrs/week for long-term partnerships.…Senior Full-Stack Engineer with 5+ years building scalable SaaS products using Python (FastAPI/Django), React/Next.js, and PostgreSQL. Experienced in integrating AI/LLM features, including RAG pipelines, OpenAI API, and vector databases. Track record of shipping MVPs from scratch, scaling platforms from hundreds to 20,000+ users, and improving conversion/performance by measurable margins. Available 30–40 hrs/week for long-term partnerships.

Semen Hoinets

Full Stack Developer, Back-End Developer, Front-End Developer, +2

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Senior Full-Stack Engineer with 5+ years building scalable SaaS products using Python (FastAPI/Django), React/Next.js, and PostgreSQL. Experienced in integrating AI/LLM features, including RAG pipelines, OpenAI API, and vector databases. Track record of shipping MVPs from scratch, scaling platforms from hundreds to 20,000+ users, and improving conversion/performance by measurable margins. Available 30–40 hrs/week for long-term partnerships.…Senior Full-Stack Engineer with 5+ years building scalable SaaS products using Python (FastAPI/Django), React/Next.js, and PostgreSQL. Experienced in integrating AI/LLM features, including RAG pipelines, OpenAI API, and vector databases. Track record of shipping MVPs from scratch, scaling platforms from hundreds to 20,000+ users, and improving conversion/performance by measurable margins. Available 30–40 hrs/week for long-term partnerships.

Available to hire

Senior Full-Stack Engineer with 5+ years building scalable SaaS products
using Python (FastAPI/Django), React/Next.js, and PostgreSQL. Experienced
in integrating AI/LLM features, including RAG pipelines, OpenAI API, and
vector databases. Track record of shipping MVPs from scratch, scaling
platforms from hundreds to 20,000+ users, and improving
conversion/performance by measurable margins. Available 30–40 hrs/week
for long-term partnerships.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Language

Ukrainian

Fluent

English

Fluent

Work Experience

Senior Full-Stack Developer at B2B SaaS (50+ employees)

January 1, 2023 - Present

Led backend architecture and REST API design using Python, Django, and FastAPI, reducing API response time by 42% and achieving 99.9% platform uptime across AWS infrastructure. Modernized the frontend with React and Next.js, optimized PostgreSQL indexing, and implemented Redis caching, scaling the product from 2,000 to 18,000+ active users. Improved onboarding flow and subscription billing, increasing conversion rates by 27% and dashboard engagement by 31%. Integrated OpenAI API and built a RAG pipeline with pgvector and LangChain to power an in-app AI assistant, reducing support ticket volume by ~30%. Containerized the full application stack with Docker and Kubernetes on AWS EKS; implemented blue-green deployments via GitHub Actions CI/CD, reducing deployment downtime to near zero. Wrote 300+ unit and integration tests using pytest and React Testing Library, reaching 85% coverage and cutting regression bugs by 40%. Mentored 2 junior engineers, led sprint planning, and collaborated with product and design to define technical roadmap.