Senior Software Engineer - Browser Extensions

About the role

The Senior Software Engineer - Browser Extensions will own the architecture and implementation of Securly's onboard filtering engine - building a local policy cache and real-time filtering decision engine inside the Chrome extension that moves filtering decisions on-device, improving speed, reliability, and bypass resistance for millions of students on Chromebooks. You will design and build the system that eliminates the cloud round-trip for 80% of filtering decisions: a local policy cache with delta sync, a filtering decision engine running inside the MV3 service worker, and the bypass prevention layer that ensures the security model is not exploitable. At L5, this role carries additional strategic weight. Google's Filter and Monitor platform shift is moving ChromeOS toward native Content Filtering APIs and away from browser extensions as the primary enforcement point. You will track this transition, evaluate its implications for Securly's extension strategy, and surface architectural recommendations - not just implement the current plan. Level: L5_____ Experience: 8-15 Years_____ Location: Pune, India_____ Work Type: Hybrid (2 days onsite)_____ Reports To: Filter Engineering Manager

Responsibilities

• Own the architecture of the onboard filtering engine: local policy cache, delta sync protocol, filtering decision engine, and bypass prevention layer.
• Architect and implement the local policy cache: delta sync protocol, TTL management, cache invalidation logic, and graceful cloud fallback.
• Build the onboard filtering decision engine in the MV3 service worker: domain matching, URL categorization, iframe detection using DOM context, and allow/block decisions.
• Implement and harden bypass prevention: same-origin policy, CSP, CORS, iframe sandboxing, content script/page context boundaries, and timing-based attack vectors.
• Track Google's Filter and Monitor platform evolution (ChromeOS Content Filtering APIs); write architectural memos evaluating implications for Securly's extension strategy.
• Lead the transition and implementation of new filtering features using TypeScript and modern JavaScript within the MV3 framework.
• Optimize extension performance to add negligible latency on consumer-grade student Chromebook hardware; define and enforce performance budgets.
• Mentor Ashish M (L4) and new extension hires: substantive code reviews, pair on security model design, drive team understanding of bypass threat vectors.
• Manage chrome.storage.local within platform limits; evaluate IndexedDB for policy cache requirements that exceed those limits.
• Skills & Requirements

Requirements

• TypeScript & JavaScript mastery - expert-level: async/await, Promises, event-driven architecture, memory management in long-running service workers. 5+ years at this level.
• Chrome Extension development (MV3) - deep production experience with Manifest V3, service workers, content scripts, chrome.storage, and declarativeNetRequest / webRequest APIs.
• Browser security model - thorough understanding of same-origin policy, CSP, CORS, iframe sandboxing, and the content script/page context boundary.
• Security-first architecture - proven ability to enumerate attack surfaces before writing the first line of code. L5 means you define the threat model.
• Local caching / offline-first architecture - delta sync, TTL management, cache invalidation design, chrome.storage.local limits, and IndexedDB.
• Technical communication - written ADRs, threat model documents, and platform evaluation memos that inform cross-team strategy.
• Strongly Preferred
• Performance profiling - Chrome DevTools profiling for extension impact on page load latency and memory on low-end Chromebook hardware.
• Web filtering / content classification - URL categorization, domain matching, iframe content detection, allow/block decision logic.
• Google Filter and Monitor platform - awareness of ChromeOS Content Filtering API direction and strategic implications for extension-based filtering products.
• ChromeOS / Google Admin Console - enterprise extension management, force-install behavior, Chrome policy effects on extension runtime.
• Test automation (extension testing) - Puppeteer, Playwright, or Selenium with extension loading.
• Kotlin - relevant if contributing to mobile filtering work alongside the Android engineering team.
• K-12 EdTech domain - familiarity with how schools manage Chromebook fleets and student filtering compliance requirements.
• You know how browsers actually work - not just the APIs, but the security model, the process model, and the specific ways students try to break it.
• You have shipped production Chrome extensions at scale and know what service worker memory management means on a 4GB Chromebook.
• You track platform shifts (Google F&M, ChromeOS Content Filtering API) and understand what they mean for your system's architecture.
• You produce written artifacts (ADRs, threat models, platform memos) that document your reasoning for

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