Principal UI Engineer – Design​/Developer Tools

## Principal UI Engineer – Design/Developer Tools Apply:
United States of America:
Full time:
Posted Yesterday:
JR0027436

Yahoo serves as a trusted guide for hundreds of millions of people globally, helping them achieve their goals online through our portfolio of iconic products. For advertisers, Yahoo Advertising offers omnichannel solutions and powerful data to engage with our brands and deliver results.## A Little About UsYahoo is a global media and tech company that connects hundreds of millions of people to the things they love, from finance and sports to news and entertainment.

Our engineering teams build high-performance, accessible, and resilient digital experiences at scale.  Our team builds the core platform, collaborative canvas, and design-to-code infrastructure that engineers and designers across Yahoo use to create and ship product UI. We care about runtime latency, distributed consistency, and fast, reliable developer workflows. We work where modern frontend architecture, real-time collaboration, and AI-augmented developer tooling meet, and we aim to raise the engineering bar across the organization.  

## A Lot About You You're a seasoned Principal Engineer who cares deeply about how complex systems behave under load, under failure, and during high-concurrency collaboration. You're fluent across the entire surface: you can profile a React render tree and an AST transform pipeline in the morning, and trace a dropped CRDT sync through a Web Socket server, Redis, and Postgres in the afternoon.

You still enjoy building UI, but most of your energy goes into making the platform beneath it fast, durable, observable, and safe to change.  You think in in variants: no user edit is ever silently lost, every deploy can be safely rolled back, and regressions are caught in CI before they reach production. You treat AI tools as collaborators and as building blocks in your systems, not just as typing accelerators.

You communicating clearly with cross-functional partners.  ## Responsibilities
* Platform Architecture & Core

Infrastructure: Own the architecture, scalability, and uptime of our real-time collaboration server, Postgres-backed persistence layer, background jobs, and the APIs that sit on top of them.
* Collaborative Systems & Data Integrity:
Design, harden, and evolve multi-user editing built on CRDTs (Yjs). Guarantee reliable sync, reconnection, conflict handling, undo/redo, and save durability, so users' work is never silently lost across disconnects, deploys, or branch switches.
* AI-Augmented Developer Tooling & Agent Interfaces:
Architect and maintain agent-ready interfaces, Model Context Protocol (MCP) servers, and automated pipelines that let AI coding agents and developers safely inspect, generate, and change design systems and codebases.
* Performance & Canvas Engineering:
Profile and optimize end-to-end bottlenecks: interactive canvas rendering, frame rates, hydration and bundle payloads, query cost, memory footprint, and server event-loop health. Build performance benchmarks and enforce regression budgets in CI.
* Developer Infrastructure & Monorepo Operations:
Steer the evolution of our large Type Script monorepo, CI/CD pipelines, automated testing, and preview, staging, and production environments so shipping stays fast, reproducible, and safe.
* Observability & Systemic Resilience:
Define SLOs, metrics, structured logging, and real-time alerting. Champion incident management, lead blameless post-incident reviews, and turn root causes into durable, platform-level fixes.
* Security & Access Control:
Partner on authentication, authorization, and permission models across systems, branches, and files, so access rules are enforced consistently everywhere.
* UI Engineering:
Contribu…