Senior Full-Stack Engineer (Backend-Focused) - Part-time - NA/LATAM/EU

About the Company

Kynismos AI is a privacy-first tech startup based in New York, building a secure platform for users to chat with leading large language models (LLMs) like ChatGPT, Claude, and more. Our mission is simple: give users full control over their chat data — no tracking, no exposure. We’re close to launching and looking for a senior full-stack engineer to take ownership of core feature development and infrastructure enhancements.

The Role

We’re hiring a senior full-stack engineer to lead development and maintenance of our platform. You'll work directly with the CTO and take charge of building secure, scalable, and intuitive features. The role is backend-heavy but requires full-stack capability, with an emphasis on data privacy, model integrations, and infrastructure.

This is a critical role as we transition from MVP to scale, and we're looking for someone who thrives on autonomy, problem-solving, and bringing structure to fast-moving projects.

Key Responsibilities

• Lead full-stack development with focus on backend systems and integrations
• Design and implement new product features (e.g., secure document upload + chat)
• Maintain and evolve the platform architecture (web app, backend, encryption layer)
• Ensure end-to-end data privacy using encryption and secure architecture best practices
• Integrate third-party LLMs via APIs
• Optimize for performance, scalability, and auditability
• Collaborate closely with CTO and cross-functional stakeholders

Tech Stack

• Frontend: Next.js (React)
• Backend: Python (FastAPI)
• Infrastructure: AWS, Docker
• Security: End-to-end encryption, envelope encryption concepts

Requirements

• 5+ years of full-stack or backend engineering experience
• Strong Python skills, ideally with FastAPI
• Experience with Next.js or modern React frameworks
• Familiarity with AWS services and Dockerized environments
• Solid understanding of modern encryption and privacy-preserving architectures
• Independent, self-driven, and able to translate product needs into scalable code
• Comfortable working async with occasional time zone overlap
• Excellent communication and documentation skills

Nice to Haves

• Experience with LLM or chatbot integrations
• Background in building secure, regulated, or audit-ready applications
• Knowledge of database security and secure API design