Mid-Senior Fullstack Remote

Mid/Senior Full-Stack Engineer Optiveum is looking for a Mid/Senior Full-Stack Engineer for a long-term, engaging project. The cooperation is based on a B2B contract directly with Optiveum, starting ASAP. The Client You will be working for a US-based technology company that builds a live social platform connecting communities through video, audio, text, and photos, alongside an emerging multimodal intelligence platform that helps brands understand public conversations and audience sentiment. The Role This is a high-ownership role for a capable generalist who wants to ship across mobile, web, and backend product surfaces. You will own high-value features from problem framing through production while leveraging AI tools to accelerate your development workflow. While the client operates in the US, the team works highly asynchronously, requiring only occasional meetings to align. What you will do • Deliver and own features across React Native, Next.js, NestJS, TypeScript, Go and Python microservices, and GCP. • Diagnose and improve real product workflows spanning UI, APIs, data, media, background processing, and third-party services. • Strengthen the media lifecycle—including capture, upload, processing, playback, analysis, retrieval, and failure recovery—across mobile and web. • Use AI tools (e.g., Gemini, ChatGPT) as an active engineering partner for coding, testing, debugging, and documentation—verifying outputs rather than relying on it as a simple answer machine. • Write maintainable code, focused tests, useful instrumentation, and concise documentation. Expectations • Solid TypeScript/JavaScript fundamentals with substantial experience delivering and operating customer-facing mobile or web applications. • Production depth in Node.js and at least one major product surface (such as React Native or Next.js). • Working knowledge of APIs, data modeling, asynchronous workflows, testing, and cloud deployment (GCP preferred). • Ability to read, extend, and troubleshoot Go and Python microservices. • Clear written and spoken English, dependability in a remote team, and a direct, low-ego approach to problem-solving. • Nice to have: Experience with media-heavy consumer products, social/community systems, creator platforms, or in-app purchases. What is offered • Salary: 125 - 130 PLN net/h (Please note: The final B2B contract will be signed in USD at the current exchange rate). • Contract: B2B directly with Optiveum. • Start: ASAP, long-term project. • Type of work: 100% Remote from Poland. • Working hours: Full-time, flexible hours (occasional late afternoon/evening meetings required for US time zone alignment).