Principal Software Engineer

pubGENIUS is a React.js and Next.js development agency and ad-tech startup. We build websites and apps for clients across the US and Europe, specializing in Defi, fintech, healthcare, and education with occasional work in e-commerce and other verticals. Beyond client work, we operate our own high-revenue web product with a website, mobile app, and machine learning systems powering our ad-tech optimization engine. Performance is not a preference here, it is a core requirement. We are looking for a Principal Software Engineer to be the technical authority, responsible for all development, architecture decisions, and long-term technical strategy across our website, mobile app, and ML-powered ad-tech optimization systems. This is a hands-on senior role where site speed and server performance are core success metrics. You will work directly with stakeholders to set technical direction, remove bottlenecks, and ship production-grade code.

Engagement Details • Type: Full-time independent contractor • Location: Remote • Clients: US and Europe • Rate: Competitive, based on experience

What You'll Own • End-to-end technical ownership of a high-revenue web platform and mobile app • Architecture design and long-term technical strategy • Server-side rendering pipeline using Node.js, Fastify 5, and React 19 • Data layer across MySQL and BigQuery • GCP infrastructure including Cloud Run, Cloud Build, and Global Load Balancer • Ad-tech integrations • Performance optimization at scale, where every millisecond counts • ML pipeline maintenance and optimization for ad-tech performance