Role Overview

Unidos Technology is seeking a highly skilled Senior JavaScript Engineer with 3 to 6 years of experience. This role is pivotal in enhancing our Real User Monitoring (RUM) solutions, focusing on application performance and user experience. You will be instrumental in developing and refining lightweight JavaScript agents designed to capture critical performance metrics, errors, and user interactions across modern web applications.

Responsibilities

• Design and develop efficient JavaScript-based monitoring agents for capturing browser performance metrics, errors, and user interactions.
• Leverage browser performance APIs such as Navigation Timing, Paint Timing, Long Tasks, and Performance Observer to track key performance indicators.
• Implement support for Core Web Vitals (LCP, FID, CLS, INP) and other industry-standard KPIs to ensure optimal web performance.
• Ensure monitoring agents are lightweight, highly efficient, and non-intrusive to the end-user experience.
• Collaborate closely with backend and APM teams to effectively correlate frontend performance traces with backend monitoring data.
• Stay abreast of the latest web performance standards and W3C specifications to drive innovation.

Must-Have Skills

• A minimum of 3 years of professional JavaScript/TypeScript development experience.
• Strong expertise in browser APIs and event-driven programming paradigms.
• Proven hands-on experience with performance measurement and optimization techniques in web applications.
• Solid understanding of Core Web Vitals and comprehensive knowledge of web performance monitoring best practices.
• Familiarity with ensuring cross-browser compatibility and proficiency with web debugging tools.
• Experience working with at least one major frontend framework (React, Angular, or Vue).
• Knowledge of compression techniques such as gzip and brotli.
• Exposure to Real User Monitoring (RUM) or frontend monitoring tools (e.g., New Relic, Datadog RUM, Dynatrace, Sentry).

Nice-to-Have Skills

• Experience in building or contributing to JavaScript SDKs or agents.
• Knowledge of Web Workers, Service Workers, and WebSockets.
• Familiarity with Open Telemetry for frontend instrumentation.
• Understanding of privacy and compliance considerations in telemetry, including PII masking and GDPR.
• Experience with session replay libraries and their customization.
• Prior contributions to observability, analytics, or APM solutions are highly valued.