Senior JavaScript Engineer

We are looking for a

Senior JavaScript Engineer

with a strong background in frontend technologies and a keen interest in

application performance and user experience monitoring

. This role focuses on building and enhancing our

Real User Monitoring (RUM) solutions

, which capture performance, errors, and user interactions across modern web applications.You will work on developing efficient, low-overhead JavaScript agents that run in the browser and provide deep visibility into how real users experience applications.

Responsibilities

• Design and develop JavaScript-based monitoring agentsthat capture performance metrics, errors, and user interactions in the browser.
• Work with browser performance APIs(Navigation Timing, Paint Timing, Long Tasks, Performance Observer) to track key metrics.
• Implement support for Core Web Vitals(LCP, FID, CLS, INP) and other industry-standard KPIs.
• Ensure that monitoring agents are lightweight, efficient, and non-intrusive.
• Collaborate with backend/APM teams to correlate frontend traces with backend monitoring data.
• Implement error monitoring, crash detection, and session replay integrations.
• Keep up with latest web performance standards and W3C specifications.
  

Must-Have Skills

• 3+ years of professional JavaScript/TypeScript development experience.
• Strong expertise in browser APIs�and event-driven programming.
• Hands-on experience with performance measurement and optimization in web apps.
• Solid understanding of Core Web Vitals�and web performance monitoring.
• Familiarity with cross-browser compatibility�and web debugging tools.
• Experience with one or more frontend frameworks (React, Angular, Vue).
• Knowledge of compression techniques (gzip, brotli).
• Exposure to RUM or frontend monitoring tools�(New Relic, Datadog RUM, Dynatrace, Sentry, etc.).
  

Nice-to-Have Skills

• Experience building or contributing to JavaScript SDKs/agents.
• Knowledge of Web Workers, Service Workers, WebSocket's.
• Familiarity with Open Telemetry for frontend instrumentation.
• Understanding of privacy and compliance�in telemetry (PII masking, GDPR considerations).
• Experience with session replay libraries�and customization.
• Prior contributions to observability, analytics, or APM solutions.