Lead Frontend Engineer (IC4 / Staff-track) on the Web Platform group at Northwind Workforce, a profitable HRIS/payroll/time-tracking platform serving ~4,200 mid-market businesses. The role owns the technical direction of a Next.js 14 monorepo (~2.4M lines of TypeScript, ~110 internal packages) underpinning all product surfaces. Responsibilities include driving the Pages Router to App Router migration, owning the platform-level performance budget (LCP, INP, CLS, custom metrics), acting as senior FE technical reviewer for cross-cutting design decisions, mentoring senior engineers across the company, and authoring Lead Engineer Proposals (LEPs) that set the 6–18-month frontend technical roadmap. The team consists of 14 engineers across 3 squads, 2 designers, and 1 staff product manager. The company operates a written-first, no-hero culture with genuine schedule flexibility around a core 10:00–15:00 London overlap window.