Senior Front End Engineer

TEKsystems•San Francisco, CA

1d•$160,000 - $200,000•Hybrid

About The Position

As a SR. Frontend Engineer, Ketch SDKs, you’ll own the runtime that powers the modern internet. You’ll design and maintain SDKs that process millions of events per day and emit billions of signals to platforms like Google, Meta, Snowflake, Datadog, and Full Story enabling data collection that respects user choices while powering the modern ad-tech ecosystem. Every network request, every consent signal, every event flows through the infrastructure you build. If Ketch ever goes down, major platforms you use daily may go down with it. The stakes are real. This is infrastructure at an impossible scale, in the hardest runtime environment imaginable. You’ll tackle performance, privacy, and reliability head-on, building systems that can’t fail and architectures that ripple through Fortune 500 production environments. We operate with deep personal ownership which means that you’ll solve problems from first principles, drive end-to-end solutions, and define the technical direction for client-side data governance at scale. You’ll design SDKs used by thousands of engineers, integrating with the entire web and mobile stack, shaping the backbone of a free and fair internet.

Requirements

Deep expertise in JavaScript & TypeScript (ES6+), browser APIs, event loops, closures, and high-performance client-side coding across diverse runtime environments.
Proven experience building SDKs and JavaScript tags deployed on customer websites, integrating with internal and external platforms under production pressure.
Mastery of browser architecture and client-side systems: rendering pipeline, network stack, storage APIs, cross-origin communication, and deterministic data flow governance.
Performance and reliability wizardry: profiling, benchmarking, optimizing, and debugging async race conditions across distributed client-side systems.
Systems thinking and build tooling experience: Webpack, Rollup, ESBuild, ESM/CommonJS/UMD, polyfills, and managing browser inconsistencies or third-party script conflicts.
Collaboration, mentorship, and product-minded ownership: articulate technical decisions, influence stakeholders, drive pragmatic solutions, and elevate teams through code reviews and knowledge sharing.
Front End React
SDK
Excellent communication skills, dynamic personality
Ability to work in a fast-paced start-up environment
Recent/extensive experience in permanent roles to ensure long-term stability and commitment
Must be authorized to work in the United States without sponsorship.

Nice To Haves

mobile SDKs (iOS/Android/React Native), ad-tech
Start-up experience highly preferred

Responsibilities

Design and evolve the core Ketch SDK runtime for consent orchestration, event tracking, rule evaluation, and platform integration at massive scale.
Optimize SDK performance under impossible constraints and enforce deterministic client-side data governance across 50+ browsers/OS combinations, intercepting and managing network requests, cookies, and storage.
Build APIs and tooling for thousands of engineers, making complex integrations simple, secure, and impossible to misuse.
Extend SDKs for custom integrations, multi-platform routing, adtech connectivity, and AI-driven privacy telemetry.
Simulate real-world network interactions with emulators and pipelines that feed AI models for privacy risk detection.
Collaborate across product, design, and customer success, mentor engineers, and drive architectural excellence across the frontend team.