Senior Frontend Developer - Phantom

Stay22•Montreal, QC

7d•Onsite

About The Position

As a Senior Frontend Developer on the Phantom squad, you will play a key role in advancing our embedded widget and affiliate platform. Your mission will be to streamline browser execution and ensure high performance of our scripts across diverse websites. You will design mechanisms for privacy-conscious session tracking and fingerprinting, and take ownership of the full script lifecycle – from load optimization to event handling and error recovery. Working closely with product and engineering leads, you will help shape and maintain the core infrastructure that powers Stay22’s embeddable products, ensuring they run reliably under real-world constraints.

Requirements

English proficiency is required for daily communication with international colleagues and direct reports.
Deep hands-on experience with vanilla and ES6+ JavaScript or TypeScript without relying on frameworks (no React/Vue/etc. for core logic)
Strong knowledge of the browser event loop, DOM API, CSSOM, rendering pipeline, and how to optimize for First Contentful Paint (FCP), Largest Contentful Paint (LCP), etc.
Proficiency with Node.js for building APIs and web scrapers; experience with Python-based scraping is a plus. Familiarity with HTTP, REST/JSON, and proxies
Understanding of browser fingerprinting methods and privacy considerations (e.g. cookie/session management, CORS, GDPR). This is a big asset
Bachelor’s or Master’s in Computer Science (or equivalent) is a plus, or equivalent professional experience in software development

Nice To Haves

Contributions open source or projects GitHub appreciated.
Contributions open source or projects GitHub appreciated.

Responsibilities

Continuously improve the load time and execution efficiency of our browser scripts (minification, caching, lazy loading, etc.)
Create robust methods for injecting content and widgets into arbitrary websites (e.g. automating DOM manipulation, handling dynamic page layouts)
Implement reliable client-side event handlers to track user interactions with embedded elements, ensuring accurate data capture
Develop and integrate fingerprinting techniques to distinguish and track user sessions across domains in a privacy-aware way
Build and maintain Node.js/Python-based scrapers to collect data from partner websites or APIs when needed; design fallback data sources for resiliency
Troubleshoot and adapt our runtime logic for real-world usage, including handling unexpected page structures or third-party script conflicts
Own the entire embedded product stack (scripts, SDKs, APIs) and collaborate with other teams to integrate updates and new features smoothly