Javascript Engineer

Join our growing engineering team as a JavaScript Engineer. In this deeply technical role, you will be responsible for building and maintaining a high-performance JavaScript SDK that is embedded across a wide network of publisher and ad platform integrations. You will collaborate closely with the security research team and have the opportunity to work from anywhere in the world.

• Co-own the design, development, and ongoing maintenance of Confiant's client-side JavaScript SDK with your teammates.
• Build and optimize SDK internals for maximum runtime performance — minimizing execution time, memory footprint, and impact on page load across diverse publisher environments.
• Translate security threat intelligence (e.g., new malvertising techniques, ad injection patterns) into SDK-level detection and blocking logic.
• The ideal candidate has a genuine passion for the craft of JavaScript at a systems level: understanding the browser runtime deeply, obsessing over payload size and execution cost, and building SDK distribution and versioning strategies that scale cleanly across a large, diverse customer base
• Experience with SDK distribution patterns — versioning strategies, CDN delivery, backward compatibility, and graceful degradation
• Proven experience building, shipping, and maintaining JavaScript SDKs or embeddable scripts at production scale
• Engineer IV (Staff): 6+ years of experience, with a track record of leading the technical direction of a library or SDK product. Comfortable operating as a force multiplier across the engineering team and interfacing effectively with product stakeholders
• Proficiency with modern JavaScript tooling: bundlers (Webpack, Rollup, esbuild), transpilers (Babel/SWC), and testing frameworks (Jest, Playwright, or similar)
• Deep familiarity with browser security models, including same-origin policy, CSP, and cross-origin isolation
• Expert-level JavaScript (ES6+) with deep knowledge of browser internals — the event loop, memory model, garbage collection, and execution context
• Engineer V (Staff): Minimum of 8+ years of experience and significant maturity solving complex problems across various technical domains, communicating with/through Product and being a force multiplier for your engineering team as well as proven experience in setting engineering practices and principles within a working environment
• Demonstrated ability to optimize for performance: bundle size, parse time, runtime efficiency, and network impact
• Strong understanding of how JavaScript executes within third-party and sandboxed environments (iframes, ad slots, cross-origin contexts)
• Experience in AdTech, including familiarity with ad serving infrastructure, tag management, or programmatic advertising concepts
• Background in security engineering, threat detection, or malware analysis
• Experience instrumenting client-side SDKs for telemetry and observability
• Familiarity with browser automation tools (e.g., Puppeteer, Playwright) for testing ad environments