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 t o 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 Must-Have Qualifications These are non-negotiable. Please only apply if you have strong, production-proven experience in all of the following: Node.js with TypeScript in production React in a server-side rendering context MySQL including database design, query optimization, and ORM usage BigQuery for querying and managing large-scale datasets GCP with hands-on experience in Cloud Run, Cloud Build, Cloud SQL, and Load Balancing (GCP certification is a significant bonus) Nice-to-Have Experience Ad-tech industry experience including ad serving, yield optimization, and programmatic advertising Affiliate marketing experience, particularly with Anura and Everflow Cloudflare including CDN configuration, caching strategies, and Workers Fastify, especially Fastify 5 patterns Flutter for mobile app contribution Golang or Rust for high-performance service work Machine learning applied to ad-tech optimization (not LLMs or agents) Experience in fintech, Fully remote work Flexible hours Paid vacation and sick days Application Process: We do not review applications via LinkedIn DMs or email. Please apply through the application link. We do not work with staffing agencies or third-party recruiters. Direct applicants only. pubGENIUS is an Equal Opportunity Employer; 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.