Type: Full-time independent contractorpubGENIUS 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.OverviewWe 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.Engagement DetailsType: Full-time independent contractorHours: Full-time commitment expectedLocation: Remote (US, Canada, UK, Ireland or Netherlands)Clients: 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 integrations including Google Ad Manager, GTM, GTag, and GPT.jsPerformance optimization at scale, where every millisecond countsML pipeline maintenance and optimization for ad-tech performanceRequirementsMust-Have QualificationsNode.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 bonusNice-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 DeFi, crypto, NFT, blockchain, fintech, or healthcare verticalsBenefitsFully remote workFlexible hoursPaid vacation and sick daysApplication ProcessWe 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.
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