Senior Lead Machine Learning Engineer (Agentic AI)

TL;DR

Senior Lead Machine Learning Engineer (Agentic AI): Architect, develop, and scale next-generation agentic intelligence and AI agent platforms with an accent on LLM training, evaluation, runtime orchestration, and safety. Focus on building multi-agent systems, training aligned LLMs, engineering backend infrastructure, and leading cross-functional teams.

Location: Lisbon, Portugal (onsite)

Company

Upwork Inc. is a global AI-powered work marketplace connecting businesses with highly skilled talent worldwide, enabling business transformation and workforce scaling.

What you will do

• Design and implement multi-agent systems with robust guardrails and recovery strategies.
• Lead LLM training, alignment, evaluation, and safety tuning for agent workflows.
• Architect and ship backend infrastructure for low-latency inference, orchestration, and developer APIs.
• Optimize cost, performance, and reliability of AI agent services.
• Provide technical leadership, mentor senior engineers, and influence product roadmaps.
• Publish internal guidance and contribute to technical content and reference architectures.

Requirements

• Location: Must be based in Lisbon, Portugal (onsite)
• Senior experience in applied ML and ML systems with LLM-powered product delivery.
• Hands-on expertise in LLM adaptation, data curation, and safety guardrails.
• Strong software fundamentals in distributed systems, microservices, and APIs.
• Proficiency in Python; knowledge of Go, Java, or JavaScript is a plus.
• Experience designing evaluation suites and managing cost, latency, and reliability trade-offs.

Culture & Benefits

• Opportunity to work in Upwork’s first international operational hub in Lisbon.
• Competitive benefits through partner employment initially, with potential transition to Upwork employment.
• Access to Upwork’s resources, culture, and growth opportunities.
• Commitment to diversity, inclusion, and equitable workforce.