Senior Applied AI Engineer

Proofpoint; Denver (CO); On-site; USD 153,000 - 224,000; Full time

Benefits offered by this job

Competitive compensation

Comprehensive benefits

Flexible work environment

Annual wellness and community outreach

Job summary

Proofpoint is seeking a Senior/Staff Applied AI Engineer to own a line of research from framing questions to building experiments and measuring results. You’ll contribute to an Applied AI Research team, turning challenging questions into evidence-based solutions and deploying them to production where they’ll be monitored in live environments.

You’ll tackle real-world problems using hosted or self-hosted models, fine-tuning and evaluation, with a strong emphasis on Python, ML fundamentals, and

Qualifications

• 5+ years building software and ML systems, with recent hands-on work on LLM systems that went past the prototype stage.
• Experience building agents that do real work, and you’ve dealt with what goes wrong when they run for a long time.
• Experience with third‑party model APIs and open‑weight models (we run on our own GPU fleet)
• Experience with Kubernetes inference platform, Flyte for orchestration, LiteLLM / Langfuse and internal tooling for evaluation and tracing.
• Experience building evals that gave you a real answer, and you know how easily they can mislead.
• Experience getting strong results out of frontier models, hosted or self‑hosted.
• Strong Python and solid ML fundamentals.
• Experience with Claude Code, Cursor or similar, used daily, without lowering your standard for correctness and tests.

Responsibilities

• Answer hard questions with evidence. Take a question nobody has answered yet. Make it testable, set a baseline, run the smallest experiment that settles it, and come back with an answer the company can act on.
• Build systems that improve themselves. A lot of our agentic work runs in long loops—run an evaluation, study the results, produce a better version, run it again.
• Make agent behaviour measurable. Extend our evaluation platform so we can tell whether an agent is genuinely good.
• Work across hosted and self-hosted models. You’ll help us work out which jobs suit which, including GPU fleet deployments.
• Improve how we build with coding agents. You’ll help our engineers get more out of them.
• Start from real problems. Spend time with stakeholders and turn what you hear into research worth doing.
• Put working things in people’s hands. Build prototypes, playgrounds and APIs so stakeholders can try an idea themselves.
• Help get it into production. Advise the team deploying it on the AI side and monitoring such systems.
• Help the team get better. Mentor engineers, share what you learn, and help the team ask better questions.

Skills

Python

LLM systems

Agent systems

ML fundamentals

Research

Tools

Kubernetes inference platform

Flyte

LiteLLM

Langfuse

Job description

About Us

Proofpoint is a global leader in human- and agent-centric cybersecurity. We protect how people, data, and AI agents connect across email, cloud, and collaboration tools. Over 80 of the Fortune 100, 10,000 large enterprises, and millions of smaller organizations trust Proofpoint to stop threats, prevent data loss, and build resilience across their people and AI workflows. Our mission is simple safeguard the digital world and empower people to work securely and confidently. Join us in our pursuit to defend data and protect people.

How We Work

At Proofpoint you’ll be part of a global team that breaks barriers to redefine cybersecurity guided by our BRAVE core values

• Bold in how we dream and innovate
• Responsive to feedback, challenges and opportunities
• Accountable for results and best in class outcomes
• Visionary in future focused problem-solving
• Exceptional in execution and impact

The Role

AI is moving faster than any single product team can keep up with. For a security company, the hard question isn’t “can a model do this?” It’s which approach actually works, what it costs, how fast and reliable it is, and whether it’s worth building at all. That’s what this team answers. We’re an Applied AI Research team, and research is our product. We take important questions the company can’t yet answer and turn them into evidence people can act on.

As a Senior/Staff Applied AI Engineer, you’ll own a line of research from start to finish frame the question, build what’s needed to answer it, measure honestly, and reach a decision. When something is ready to move to another team, you’ll help them deploy it well, advising on the AI side and on how to monitor it once it’s live. Sometimes the answer is “this works, here’s the proof.” Sometimes it’s “this won’t work, and we found out in three weeks instead of six months.” Both count as success here.

What you’ll do

• Answer hard questions with evidence. Take a question nobody has answered yet. Make it testable, set a baseline, run the smallest experiment that settles it, and come back with an answer the company can act on.
• Build systems that improve themselves. A lot of our agentic work runs in long loops run an evaluation, study the results, produce a better version, run it again. You’ll build systems that improve on their own and recover when they go wrong.
• Make agent behaviour measurable. Extend our evaluation platform so we can tell whether an agent is genuinely good - task suites, regression checks, and honest tradeoffs between quality, cost and speed. It’s something we build and maintain for the whole company.
• Work across hosted and self-hosted models. Most of what we do runs on third-party model APIs. We also serve open-weight models on our own GPUs and are pushing further into fine-tuning and efficient serving. You’ll help us work out which jobs suit which.
• Improve how we build with coding agents. We use coding agents every day and benchmark them against our own codebases. You’ll help our engineers get more out of them.
• Start from real problems. Spend time with stakeholders, understand their problems rather than collecting feature requests, and turn what you hear into research worth doing.
• Put working things in people’s hands. Build prototypes, playgrounds and APIs so stakeholders can try an idea themselves and learn alongside us. Often that’s how the decision gets made.
• Help get it into production. When something works, we don’t just hand it over. You’ll advise the team deploying it - on the AI side, and on how to monitor and understand the system once it’s running.
• Help the team get better. Mentor engineers, share what you learn, and help the team ask better questions.

What we’re looking for

• 5+ years building software and ML systems, with recent hands‑on work on LLM systems that went past the prototype stage.
• Experience building agents that do real work, and you’ve dealt with what goes wrong when they run for a long time.
• Experience with third‑party model APIs and open‑weight models (we run on our own GPU fleet)
• Experience with Kubernetes inference platform, Flyte for orchestration, LiteLLM / Langfuse and internal tooling for evaluation and tracing.
• Experience building evals that gave you a real answer, and you know how easily they can mislead.
• Experience getting strong results out of frontier models, hosted or self‑hosted.
• Strong Python and solid ML fundamentals.
• Experience with Claude Code, Cursor or similar, used daily, without lowering your standard for correctness and tests.

Preferred

• Experience fine‑tuning or serving open‑weight models
• Experience with automated prompt and pipeline optimization
• Experience with multi‑GPU serving and or MCP and tool protocols
• Previous cybersecurity experience such as phishing or threat detection
• Open‑source contributions or publications.

Why Proofpoint?

• Competitive compensation
• Comprehensive benefits
• Career success on your terms
• Flexible work environment
• Annual wellness and community outreach days
• Always on recognition for your contributions
• Global collaboration and networking opportunities

Our Culture

Our culture is rooted in values that inspire belonging, empower purpose and drive success-every day, for everyone.

We encourage applications from individuals of all backgrounds, experiences, and perspectives. If you need accommodation during the application or interview process, please reach out to [e-mail].

Base Pay Ranges

SF Bay Area, New York City Metro Area

Base Pay Range 200,300.00 - 293,810.00 USD

California (excludes SF Bay Area), Colorado, Connecticut, Illinois, Washington DC Metro, Maryland, Massachusetts, New Jersey, Texas, Washington, Virginia, and Alaska

Base Pay Range 167,300.00 - 245,355.00 USD

All other cities and states excluding those listed above

Base Pay Range 152,900.00 - 224,235.00 USD