Lead Machine Learning Engineer / Applied Scientist

We’re looking for a Lead Machine Learning Engineer / Scientist to join our Algorithms and Research team within the ML & AI organization. In this role, you will help shape the reinforcement learning systems that power high-impact experiences across Upwork, including Search & Recommendations and Uma, our AI assistant. You will design and scale advanced reasoning, planning, and retrieval systems that connect research innovation to production outcomes. This is a hands‑on, high‑ownership role for someone excited to push the frontier of RL, autonomous agents, and applied machine learning on a fast‑evolving platform.

This role will require 3 days in office once we have an office open.

Responsibilities:

Design and advance reinforcement learning systems for reasoning and planning, including approaches inspired by Monte Carlo Tree Search, policy and value networks, and modern agentic decision‑making methods.

Build scalable retrieval and decisioning architectur...