Are you an SDE II who thrives on end-to-end ownership, gets energized by problems where correctness actually matters, and wants to work on systems that are actively being reimagined and not just maintained? This role might be for you. On Fee Tech, you will own systems that 2+MM sellers depend on daily to understand, predict, and act on their economics. The work is genuinely end-to-end: you design, build, ship, and operate. Our systems process ~68.5B transactions and used across 23 countries. The engineering model is changing fast: we are rebuilding how fee policy is expressed, deployed, and validated using AI agents, formal verification (SMT), and self-improving RL loops. You will work alongside senior and principal engineers, product managers, applied scientists, and ML engineers across the full fee lifecycle — from the Fee Calculation Engine through ML-based item classification to seller-facing AI surfaces and the agentic infrastructure beneath them. If you are the kind of engineer who wants to see the direct impact of what you ship, you will see it here. Key job responsibilities Design and build distributed systems. Deliver features end-to-end: own requirements scoping, technical design, implementation, code review, testing, launch, and operational monitoring for your workstreams — from initial design doc through production. Operate AI-native engineering practices: use AI-assisted coding, multi-agent workflows, and agentic code review tools as your default mode of software delivery. Build and maintain agentic systems with a focus on correctness, latency, and self-improvement loops. Drive operational excellence: participate in oncall rotation, resolve incidents, reduce MTTR, contribute to postmortems and preventive action items, and build tooling that reduces KTLO burden for the team. Collaborate across disciplines: partner with product managers defining seller experience roadmaps, UX designers shaping how sellers interact with fee surfaces, data and applied scientists building ML models for fee classification and seller economics analysis, and business stakeholders across WW Global Selling, FBA, and Finance. Contribute to technical strategy: write design documents and architecture proposals that are reviewed and challenged by senior engineers; participate actively in architectural discussions around the three-year Agentic Architecture Plan. Mentor and support peers: review code with a high bar, share feedback constructively, and help junior engineers grow through pairing, design reviews, and documentation.