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 DetailsType: Full-time independent contractorLocation: RemoteClients: US and EuropeRate: Competitive, based on experienceWhat You'll OwnEnd-to-end technical ownership of a high-revenue web platform and mobile appArchitecture design and long-term technical strategyServer-side rendering pipeline using Node.js, Fastify 5, and React 19Data layer across MySQL and BigQueryGCP infrastructure including Cloud Run, Cloud Build, and Global Load BalancerAd-tech integrationsPerformance optimization at scale, where every millisecond countsML pipeline maintenance and optimization for ad-tech performanceRequirementsMust-Have QualificationsThese are non-negotiable. Please only apply if you have strong, production-proven experience in all of the following:Node.js with TypeScript in productionReact in a server-side rendering contextMySQL including database design, query optimization, and ORM usageBigQuery for querying and managing large-scale datasetsGCP with hands-on experience in Cloud Run, Cloud Build, Cloud SQL, and Load Balancing (GCP certification is a significant bonus)Nice-to-Have ExperienceAd-tech industry experience including ad serving, yield optimization, and programmatic advertisingAffiliate marketing experience, particularly with Anura and EverflowCloudflare including CDN configuration, caching strategies, and WorkersFastify, especially Fastify 5 patternsFlutter for mobile app contributionGolang or Rust for high-performance service workMachine learning applied to ad-tech optimization (not LLMs or agents)Experience in fintech,BenefitsFully remote workFlexible hoursPaid vacation and sick daysApplication Process:We do not review applications via LinkedIn DMs or email. Please apply through the application linkWe do not work with staffing agencies or third-party recruiters. Direct applicants onlypubGENIUS 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.