About the role

JavaScript Engineer developing high-performance client-side SDK for malvertising detection at Confiant. Focused on building resilient JavaScript that neutralizes threats in real-time within ad environments.

Responsibilities

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
Develop robust SDK versioning, deployment, and distribution strategies that allow seamless rollouts and updates across a large, heterogeneous customer base
Translate security threat intelligence (e.g., new malvertising techniques, ad injection patterns) into SDK-level detection and blocking logic
Instrument the SDK for observability — ensuring signals, errors, and detection events are surfaced reliably back to Confiant's backend systems
Collaborate with the security research team to stay ahead of evolving malvertiser methods and rapidly prototype new detection heuristics
Conduct rigorous performance profiling, benchmarking, and regression testing to ensure SDK changes never degrade customer experience
Establish and champion SDK engineering best practices including testing strategies, documentation standards, and release processes
Debug complex, time-sensitive production issues occurring within live ad environments across a wide range of browsers and platforms

Expert-level JavaScript (ES6+) with deep knowledge of browser internals — the event loop, memory model, garbage collection, and execution context
Strong understanding of how JavaScript executes within third-party and sandboxed environments (iframes, ad slots, cross-origin contexts)
Proven experience building, shipping, and maintaining JavaScript SDKs or embeddable scripts at production scale
Demonstrated ability to optimize for performance: bundle size, parse time, runtime efficiency, and network impact
Experience with SDK distribution patterns — versioning strategies, CDN delivery, backward compatibility, and graceful degradation
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