Staff Software Engineer, Ads ML

Whatnot Inc.; Kraków; Hybrid; PLN 260,000 - 420,000; Full time

Benefits offered by this job

Holiday policy

Health insurance options

Work from home support

Home office setup allowance

Cell phone & internet allowance

Wellness allowance

Childcare allowance

Parental leave

Job summary

Whatnot is seeking a Staff Software Engineer to shape the technical foundation of our advertising marketplace. You will architect high-throughput backend systems for auctions, bidding, and ranking, and lead cross-functional initiatives with product and ML teams.

You will own performance, scalability, and reliability, drive architectural decisions, and mentor engineers. This remote role supports a global team across multiple hubs, including Europe, with opportunities to influence internationally.

Qualifications

• Bachelor’s degree in CS or equivalent work experience.
• 8+ years backend/distributed systems engineering (Staff) or 10+ years (Senior Staff).
• Strong mastery of distributed systems: consensus, partitioning, replication, coordination, sharding.
• Deep experience with high-throughput, low-latency services and stream processing (Kafka, Flink).
• Strong software design, algorithmic, and data-structure skills.
• Proficiency in one or more languages (Python, Go) and scripting.
• Experience with messaging, caches (Redis, RocksDB), time-series stores, and data pipelines.
• Proven track record of leading architecture and scaling core systems under high load in ads/ranking/ML serving.
• Excellent communication skills and ability to influence cross-organizational stakeholders.
• Proven track record of delivering features end-to-end quickly without sacrificing quality.
• Strong ownership instincts to drive from inception to production.
• Ability to quickly pick up new technologies.
• Startup experience in high-growth environments (nice to have).
• Experience with ads systems, infra, and international commerce (nice to have).

Responsibilities

• Architect and lead high-throughput, low-latency backend systems powering ad auctions, bidding, pacing, ranking, and delivery.
• Design auction mechanisms balancing seller value, buyer experience, marketplace efficiency, and ecosystem health.
• Build services for budget management, forecasting, experimentation, attribution, and measurement.
• Develop integrations between real-time auction services, ML models, data pipelines, and marketplace systems.
• Own performance, resilience, observability, and scalability of critical services in production.
• Define service contracts, architectural patterns, fault-isolation, and capacity plans for shared systems.
• Lead decisions for new auction and monetization capabilities and evolution of platform infrastructure.
• Partner with product and ML teams to translate marketplace problems into backend solutions.
• Lead design and code reviews, mentor senior engineers, raise engineering standards.
• Participate in incident response, root-cause analysis, and postmortems for critical systems.
• Develop the technical roadmap for auction infrastructure and tie investments to outcomes.

Skills

Distributed systems

Backend engineering

Low-latency systems

Leadership

Architecture design

Ads systems

Cross-functional collaboration

Communication

End-to-end delivery

Ownership

Learning new tech

Startup experience

International commerce

Education

Bachelor’s degree in Computer Science or equivalent

Tools

Python

Go

Kafka

Flink

Redis

RocksDB

Job description

Join the Future of Commerce with Whatnot!

Whatnot is the largest live shopping platform in North America and Europe to buy, sell, and discover the things you love. Whether it's trading cards, fashion, electronics, or live plants, our sellers are building real businesses across hundreds of categories. We're building live commerce at a scale that's never been done in the West, and there's no playbook to copy. The people here are shaping how an entirely new industry develops.

As a remote co-located team, we're inspired by our values and anchored in hubs across the US, UK, Ireland, Poland, Germany, and Australia. We move fast, stay close to our users, and focus on the work that drives the most impact.

We're one of the fastest growing marketplaces and were recently named the #1 Best Startup Employer in America by Forbes. Check out the latest Whatnot updates on our news and engineering blogs and join us as we enable anyone to turn their passion into a business and bring people together through commerce.

Role

Ads is a growing engineering team dedicated to building the systems that help Whatnot sellers grow their businesses. Our products operate at the intersection of marketplace dynamics, auction mechanics, ranking, and distributed systems.

As an engineer on the Ads team, you will shape the technical foundation of Whatnot’s advertising marketplace. You’ll design auction systems that allocate limited buyer attention across sellers, balance marketplace and customer outcomes, and operate reliably at Whatnot’s scale. This includes bidding, pricing, pacing, ranking, forecasting, and real-time decision-making.

This role requires strong technical judgment, comfort navigating ambiguous domains, and the autonomy to lead foundational projects from inception through production. You’ll work closely with product, machine learning, and infrastructure teams to make sound trade-offs and ship high-impact systems quickly without compromising quality.

In this role, you will…

• Architect and lead the implementation of high-throughput, low-latency backend systems that power ad auctions, bidding, pacing, ranking, and delivery.

• Design auction mechanisms that balance seller value, buyer experience, marketplace efficiency, and long-term ecosystem health.

• Build foundational services for budget management, allocation, forecasting, experimentation, attribution, and measurement.

• Develop reliable integrations between real-time auction services, machine learning models, data pipelines, and marketplace systems.

• Own the performance, resilience, observability, and scalability of critical services throughout their production lifecycle.

• Define service contracts, architectural patterns, fault-isolation strategies, and capacity plans for systems used by multiple product teams.

• Lead technical decisions for new auction and monetization capabilities, including how experiments graduate into durable platform infrastructure.

• Partner with product and machine learning teams to translate marketplace problems into practical backend and algorithmic solutions.

• Lead design and code reviews, mentor senior engineers, and raise the engineering bar across system design, testing, deployment, and operations.

• Participate in incident response, root-cause analysis, and postmortems for critical production systems.

• Develop the technical roadmap for auction infrastructure and connect foundational investments to measurable seller, buyer, and marketplace outcomes.

You

Curious about who thrives at Whatnot? We’ve found that embodying a low ego, growth mindset, and high-impact drive goes a long way here.

As our next Staff Software Engineer you should have:

• Bachelor’s degree in Computer Science, a related field, or equivalent work experience

• 8+ years (for Staff) or 10+ years (for Senior Staff) of backend/distributed systems engineering experience.

• Strong mastery of distributed systems fundamentals: consensus, partitioning, replication, coordination, sharding, state management, etc.

• Deep experience with high-throughput, low-latency services and stream processing (e.g., Kafka, Flink, etc.).

• Strong software design, algorithmic, and data-structure skills.

• Proficiency in one or more languages (e.g., Python, Go) and scripting.

• Experience with messaging, caches (e.g., Redis, RocksDB), time-series stores, and data pipelines.

• Proven track record of leading architecture and scaling core systems under high load, especially in an ads, ranking, or ML serving context.

• Excellent communication skills, ability to influence cross-organizational stakeholders.

• Proven track record of delivering features end-to-end and can ship products and features lightning-fast without sacrificing quality.

• Strong ownership instincts — capable of driving projects from inception to production and beyond.

• The ability to pick up on new technologies very quickly.

• Startup experience at a high-growth company — working in fast-paced, rapidly evolving product environments with frequent experimentation (nice to have).

• Experience with ads systems (bidding, auction, attribution, measurement, etc.), infrastructure, and international commerce (nice to have).

Compensation

The salary range may be inclusive of several levels that would be applicable to the position. Final salary will be based on a number of factors including, level, relevant prior experience, skills, and expertise. This range is only inclusive of base salary, not benefits (more details below) or equity.

Benefits

• Generous Holiday and Time off Policy

• Health Insurance options including Medical, Dental, Vision

• Work From Home Support

  • Home office setup allowance

  • Monthly allowance for cell phone and internet

• Care benefits

  • Monthly allowance for wellness

  • Annual allowance towards Childcare

  • Lifetime benefit for family planning, such as adoption or fertility expenses

• Retirement; 401k offering for Traditional and Roth accounts in the US (employer match up to 4% of base salary) and Pension plans internationally

• Monthly allowance to dogfood the app

  • All Whatnauts are expected to develop a deep understanding of our product. We're passionate about building the best user experience, and all employees are expected to use Whatnot as both a buyer and a seller as part of their job (our dogfooding budget makes this fun and easy!).

• Parental Leave

  • 16 weeks of paid parental leave + one month gradual return to work *company leave allowances run concurrently with country leave requirements which take precedence.

Please note: Whatnot will only contact you through official @whatnot.com email addresses. If you see an email impersonating a Whatnot recruiter, please disregard and report it as spam.

EOE

Whatnot is proud to be an Equal Opportunity Employer. We value diversity, and we do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, parental status, disability status, or any other status protected by local law. We believe that our work is better and our company culture is improved when we encourage, support, and respect the different skills and experiences represented within our workforce.