[Hiring] Machine Learning Engineer, Ads Optimization & Ads Marketplace Quality @Reddit

Role Description

We are hiring Machine Learning Engineers (IC3 and 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) or Ads Marketplace Quality (ad matching, ad load, quality controls) to deliver measurable wins for advertisers and Redditors.

We are hiring at both IC3 and IC4 levels:

• IC3 MLEs are strong individual contributors who can independently own scoped projects, ship models and services, and contribute to experimentation and measurement.
• 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

• Auction, Bidding, and Pacing Systems
  • 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).
• Marketplace Quality and Optimization
  • Partner with Ads Marketplace Quality to improve ad matching and ranking by incorporating new quality and relevance signals into bidding and auction decisions.
  • Inform policies around ad load and eligibility that protect user experience while increasing high-quality ad opportunities.
  • Collaborate closely with Ads Optimization to integrate new bid strategies and pacing mechanisms into the broader ads ecosystem and measurement stack.

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