[Hiring] Machine Learning Engineer, Ads Optimization @Reddit

Role Description

We are hiring Machine Learning Engineers (IC4) to build and evolve the auction, bidding and budgeting systems that power Reddit Ads. In this role, you will:

• Design and implement optimization algorithms for auctions, bidding strategies, and pacing that balance advertiser performance, user experience, and marketplace efficiency.
• Own systems end-to-end: from problem formulation and algorithm design to experimentation, production deployment, and ongoing iteration.
• Work across Ads Optimization (bid strategies, budget optimization, pacing) to deliver measurable wins for advertisers and Redditors.

We are hiring a Senior (IC4) level: IC4 MLEs lead more complex or multi-quarter initiatives, set technical direction for key parts of the bidding/auction/pacing stack, and mentor other engineers while remaining hands-on.

Responsibilities

• Design and implement models and policies that:
• Compute bids for different optimization objectives (e.g., CPC, CPA, ROAS-based strategies).
• Pace budgets smoothly over time across accounts, campaigns, and ad groups while preventing overspend or underspend.
• Allocate spend and auction participation intelligently across segments, surfaces, and time zones.
• Translate product and marketplace goals into concrete optimization problems and constraints (e.g., ROI, revenue, delivery smoothness, fairness, and user experience).

Qualifications

• 3–5+ years of experience building, deploying, and operating machine learning systems in production (for IC4, typically 5+ years).
• Strong programming skills in Python, Java, Go, or similar languages, with solid software engineering fundamentals.
• Experience designing scalable data processing systems (e.g., Spark, Kafka, Airflow, BigQuery, Redis).
• Demonstrated ability to translate ambiguous product or business problems into solutions and to improve measurable metrics.
• Evidence of stronger math and optimization skills than a generic MLE, such as:
• Degree or equivalent background in a quantitative field (math, physics, quantitative finance, economics, operations research, or similar).
• Work experience in optimization-heavy domains (e.g., bidding/auctions, pacing, pricing, logistics optimization, quantitative finance).
• Comfort reasoning about and implementing custom optimization logic (e.g., gradient-based methods, constraint handling), not just applying black-box tooling.

Preferred Qualifications

• Experience with advertising/auction systems, online marketplaces, or search/ranking systems at scale, particularly in:
• Bidding, pacing, or budget optimization.
• Auction design, mechanism design, or marketplace quality.
• Campaign performance optimization (e.g., CTR/CVR, CPA, ROAS).
• Familiarity with large-scale, real-time decision systems and low-latency production environments.
• Background in feature engineering, model optimization, and production monitoring for ML systems.
• Experience collaborating with cross-functional partners (Product, DS, Eng) in Ads or marketplace contexts and leading projects from design through rollout.
• Advanced degree (MS or PhD) in Computer Science, Machine Learning, Operations Research, Applied Math, or a related quantitative field.

Benefits

• Comprehensive Healthcare Benefits and Income Replacement Programs.
• 401k with Employer Match.
• Global Benefit programs that fit your lifestyle, from workspace to professional development to caregiving support.
• Family Planning Support.
• Gender-Affirming Care.
• Mental Health & Coaching Benefits.
• Flexible Vacation & Paid Volunteer Time Off.
• Generous Paid Parental Leave.