Principal Software Engineer, Ads Backend Engineering

The Ads Foundations org is where Ads Engineering, Product, ML Systems, and Experimentation efforts are combined to show the best ad to Reddit users. Our responsibilities include:

• Tech Evolution of the Reddit & Ads stack - Bringing the Ads tech stacks into the future leveraging existing Reddit centralized resources (Cloud/People/Know-how) and going beyond when required by ads unique scaling and performance challenges. 
• Balancing the needs of two different customer types – advertisers and Reddit users.
• Engineering velocity & happiness - Unlock the shortest path, without compromising on quality, to build from proof of concepts to fully productionized systems using new ML models, targeting approaches and relevance measurements. We want to democratize developer velocity independently from the size or the amount of infra/system expertise a specific vertical team has.
• Cloud resources & Data observability - Standardize and apply best practices among all the vertical teams to be able to understand Cloud and Business impact for any given product launch. As we evolve as a public company, we also want to evolve our best practices when it comes to resources to teams/systems/components mapping to facilitate future refactors, optimization, and go to market initiatives.
• Cost of Revenue Tracking and Optimizations - Design, implement, and drive best practices for all development teams to ship cost efficient systems that can survive the test of time. The Ads Infrastructure team acts as the gate to validate the engineering excellence of a given system going live for millions of customers.

We are seeking a Principal Engineer to lead the technical strategy and vision for Ads Foundations at Reddit — the technical backbone powering Ads Monetization at scale. This is the most senior individual contributor role in our engineering organization, designed for those who drive not only complex systems but also organizational and industry-wide influence.

As Principal Engineer, you will set the technical direction for how Reddit’s Ads backend evolves to meet the next generation of advertiser and user needs — with a particular focus on platform architecture, scalability, reliability, and operational excellence. You will operate as a force multiplier: elevating not only our systems, but also our engineers, our org, and the industry at large.

What You’ll Do

Technical Vision & Strategy

• Define and drive the long-term technical architecture and platform strategy for Reddit Ads backend systems, anticipating future needs 3–5+ years out.
• Identify foundational gaps and emerging opportunities across Ads infrastructure, and lead strategic investments to address them.

Scale & Systems Leadership

• Architect systems that power billions of ad impressions with high reliability, low latency, and cost efficiency.
• Set standards for system design, scalability, and operational excellence that raise the bar across Reddit engineering.

Technical Stewardship

• Lead cross-org and cross-functional technical initiatives that span beyond Ads — influencing how Reddit builds backend infrastructure at scale.
• Partner deeply with Infrastructure, Data, Machine Learning, and Product teams to ensure cohesive, performant systems.

Operational Excellence

• Champion rigorous observability, reliability engineering, and cost-aware architecture practices across the Ads organization.

Mentorship & Leadership

• Coach, sponsor, and elevate Staff and Senior Engineers across the org — shaping the next generation of technical leaders.
• Model a culture of technical curiosity, deep ownership, and high standards.

Industry & Thought Leadership

• Represent Reddit’s technical brand externally through talks, blog posts, patents, or contributions to open source.
• Stay ahead of industry trends in large-scale distributed systems, ads infrastructure, and backend engineering.
  
  

Who You Might Be

• 10+ years of experience designing and operating highly scalable backend infrastructure.
  Recognized technical leader with a proven track record of driving large-scale platform transformations.
• Deep expertise in distributed systems, backend architecture, infrastructure, and performance engineering.
• Skilled at driving clarity in ambiguous spaces, influencing technical strategy across organizations.
• Exceptional collaborator and communicator — adept at aligning technical vision with business outcomes.
• Expertise in one or more general-purpose programming languages (Python, Go, Java, Rust, C++).
• Strong experience with systems observability, reliability, and operational best practices.
  
  

Bonus Points

• Experience in AdTech, real-time bidding systems, or creative management platforms.
• Experience driving infrastructure cost efficiency and performance optimization at scale.
• Contributions to technical communities or industry research.
• Prior experience with Technical Program Management for multi-year infrastructure bets.

Benefits:

• Comprehensive Healthcare Benefits and Income Replacement Programs
• 401k Match
• Family Planning Support
• Gender-Affirming Care
• Mental Health & Coaching Benefits
• Flexible Vacation & Reddit Global Days Off
• Generous paid Parental Leave  
• Paid Volunteer time off

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