Principal Software Development 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 decentralized finance (DeFi, crypto, NFT, blockchain), fintech, and healthcare, 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, who will be the technical authority, responsible for all development, architecture decisions, and long-term technical strategy across a website, mobile app, and ML-powered ad-tech optimization systems. This is a full-time independent contractor engagement. You will work hands-on at a senior level 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. Type: Full-time independent contractor Hours: Full-time commitment expected Location: Remote (US, Canada, UK, Ireland or Netherlands) 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 js Performance optimization at scale, where every millisecond counts ML pipeline maintenance and optimization for ad-tech performance js with TypeScript in production React in a server-side rendering context MySQL including database design, query optimization, and ORM usage GCP with hands-on experience in Cloud Run, Cloud Build, Cloud SQL, and Load Balancing. GCP certification is a significant bonus. Cloudflare including CDN configuration, caching strategies, and Workers Golang or Rust for high-performance service work Machine learning applied to ad-tech optimization (not LLMs or agents) Experience in DeFi, crypto, NFT, blockchain, fintech, or healthcare verticals Fully remote work Flexible hours Paid vacation and sick days employment with pubGENIUS is governed on the basis of merit, competence, and qualifications and will not be influenced in any manner by race, age, colour, gender, religion, national origin/ethnicity, veteran status, sexual orientation, marital status, gender identity, mental or physical disability, or any other legally protected status.