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...