About the role
pubGENIUS is a React.js and Next.js development agency and ad-tech startup building websites and apps for clients across the US and Europe, specializing in decentralized finance, fintech, and healthcare. Beyond client work, pubGENIUS operates its own high-revenue web product with a website, mobile app, and machine learning systems powering an ad-tech optimization engine. As Principal Software Engineer, you will be the technical authority responsible for all development, architecture decisions, and long-term technical strategy across the platform. 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, collaborating directly with stakeholders to set technical direction, remove bottlenecks, and ship production-grade code. You will own the server-side rendering pipeline using Node.js, Fastify 5, and React 19, the data layer across MySQL and BigQuery, GCP infrastructure including Cloud Run, Cloud Build, and Global Load Balancer, ad-tech integrations including Google Ad Manager, GTM, GTag, and GPT.js, performance optimization at scale, and ML pipeline maintenance and optimization for ad-tech performance.
What we're looking for
Production-proven experience with Node.js and TypeScript. Strong experience with React in a server-side rendering context. MySQL experience including database design, query optimization, and ORM usage. BigQuery experience for querying and managing large-scale datasets. Hands-on GCP experience including Cloud Run, Cloud Build, Cloud SQL, and Load Balancing — GCP certification is a significant bonus. Ad-tech industry experience including ad serving, yield optimization, and programmatic advertising is a plus. Experience with Cloudflare including CDN configuration, caching strategies, and Workers is a plus. Familiarity with Fastify, especially Fastify 5 patterns, is a plus. Flutter experience for mobile app contribution is a plus. Golang or Rust experience for high-performance service work is a plus. Machine learning experience applied to ad-tech optimization (not LLMs or agents) is a plus. Experience in DeFi, crypto, NFT, blockchain, fintech, or healthcare verticals is an advantage.