onsite
Frontend Developer - E X P E R I E N C I O U S
Frontend Engineer
Senior Frontend Engineer to architect ultra-lightweight JavaScript runtime engines, optimize web performance, and implement zero-trust security for global browser environments.
About the role
Key Responsibilities
- Architect and optimize a lightweight JavaScript runtime engine (under 15kb gzipped) for global browser injection and experiment governance
- Ensure SDK performance meets strict latency budgets (under 50ms) while maintaining LCP and CLS boundaries
- Implement zero-trust security measures including Subresource Integrity (SRI) hashes and PCI-DSS v4.0 compliant telemetry bridges
- Manage Single-Page Application lifecycles through passive, non-destructive mutation observation without disrupting host routing frameworks
- Provide technical leadership for Chrome Extension development and integration with front-end libraries
- Collaborate with UX strategy teams to bridge infrastructure requirements with user experience goals
Requirements
- 8+ years building high-traffic client-side SDKs, browser extensions, or complex web applications
- Mastery of modern vanilla JavaScript (ES6+), DOM APIs, Shadow DOM, and browser stacking contexts
- Deep understanding of web vitals, network protocols (navigator.sendBeacon), and layout shift prevention
- Familiarity with Content Security Policy (CSP) directives and threat prevention strategies
- Strong advocacy for user experience with preference for invisible code and host application precedence
Skills
vanilla javascriptdom apisshadow domweb performancecontent security policybrowser extensions