Senior Backend Engineer, International Engineering

Whatnot; Kraków; On-site; PLN 100,000 - 130,000; Full time

Job summary

Whatnot is looking for a Senior Backend Engineer in Kraków, Poland, to design and build highly scalable systems supporting millions of transactions across multiple countries. The role focuses on backend engineering, requiring strong proficiency in Python or Go, and experience with relational databases.

Responsibilities include developing operational tooling for marketplace operations and ensuring tax compliance. Candidates should have over 5 years of software engineering experience and excellent communication skills to collaborate across teams.

Qualifications

• 5+ years of professional software engineering experience.
• Strong backend engineering experience in distributed systems or large-scale platforms.
• Experience designing, operating, and scaling reliable production services.

Responsibilities

• Design and build systems that support millions of transactions.
• Develop operational tooling for efficient international marketplace operations.
• Create cross-border transaction infrastructure.

Skills

Backend engineering in distributed systems

Proficiency in Python

Strong communication skills

Tools

Relational databases

Event-driven architectures

Job description

The International Engineering team is responsible for building the operational and transactional systems that enable Whatnot to scale globally. This team focuses on everything that happens after a transaction occurs.

Responsibilities

• Cross-border transaction infrastructure
• Tax and regulatory compliance
• International post-purchase experiences
• Marketplace operational tooling and automation

As a Senior Backend Engineer, you will design and build highly scalable systems that support millions of transactions across multiple countries and regulatory environments.

Example Projects Include

• Building VAT tooling and seller-facing tax infrastructure for EU and UK markets
• Designing cross-border shipping and Delivered Duty Paid (DDP) experiences that enable international commerce
• Building systems to support market-specific requirements including Right of Withdrawal, refund automation, and regulatory compliance. Expanding Seller Protection Systems (SPS) into international markets
• Developing operational tooling that enables efficient international marketplace operations
• Partnering with internal logistics, payments, and platform teams to build durable long-term infrastructure

About You

Required

• 5+ years of professional software engineering experience
• Strong backend engineering experience in distributed systems or large-scale platforms
• Experience designing, operating, and scaling reliable production services
• Strong proficiency in Python or Go
• Experience working with relational databases and event-driven architectures
• Ability to drive projects independently from ambiguous problem statements to production launch
• Excellent communication skills and ability to collaborate across engineering, product, operations, and business stakeholders

Preferred

• Experience with payments, fintech, e-commerce, logistics, marketplace platforms, or compliance systems
• Experience building operational platforms, workflow systems, or transaction processing infrastructure
• Experience working in rapidly growing product organizations

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.