Senior JavaScript Engineer

Role Overview

Senior JavaScript Engineer

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 agents

  that 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, WebSockets

  .
• 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

  .