About This Opportunity We are building a high-performance advertising platform that integrates directly into publisher websites via a lightweight JavaScript and React-based widget. Our system renders dynamic local classified listings post-page load and is powered by a custom header bidding stack built on Prebid.js, fully deployed on Amazon Web Services. We are looking for a Senior JavaScript Engineer with strong AdTech experience (or adjacent high-performance frontend systems) to help scale and optimize our bidding infrastructure and on-page rendering engine. Key responsibilities and your contribution Architect and optimize a custom Prebid.js-based header bidding stack Build and maintain high-performance JavaScript integrations running on publisher websites Improve latency, auction efficiency, and yield optimization across ad units Develop and enhance React-based widgets that render dynamic local listings Collaborate on bidder integrations, adapters, and demand partner connections Debug complex issues across browser environments, third-party scripts, and ad exchanges Tech Stack JavaScript (ES6+), TypeScript (preferred) React (rendering layer for widgets) Prebid.js / Header Bidding AWS (Lambda, CloudFront, S3, etc.) Real-time data flows, event-driven architectures Is that you? 5+ years of JavaScript engineering experience Strong understanding of browser performance, async loading, and script executionExperience with AdTech ecosystems (Prebid, GAM, DSPs, SSPs) OR strong adjacent experience (high-scale JS, real-time systems) Familiarity with header bidding concepts (auctions, bid requests, latency tradeoffs) Experience debugging third-party script conflicts and optimizing page performance Ability to work in a fast-moving, product-driven environment Nice to have Direct experience with Prebid.js customization or bidder adapters Exposure to analytics, tracking, and attribution systems What's working at Dev.Pro like? 30 paid days off each year — use them for vacation, holidays, or personal time 5 paid sick days, up to 60 days of medical leave, and 6 paid days off for family events like weddings, funerals, or having a baby Partially covered health insurance - after probation Wellness bonus for gym memberships, sports nutrition, and similar needs #J-18808-Ljbffr