Staff Backend Engineer, Ads ML & Auctions

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

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.