Senior Software Engineer, Backend

About the role

Affirm is building transparent financial products to provide consumers with flexible payment options. This role focuses on developing the infrastructure that enables engineering teams to validate software changes with speed and reliability.

Key facts

What you'll do

• Architect and maintain systems for synthetic identities, test data management, mocking, and load testing.
• Shift testing strategy away from heavy end-to-end reliance toward component, integration, contract, and performance testing.
• Create platform tools that make production-like load testing repeatable and safe.
• Define and lead technical projects from initial concept through implementation and operational ownership.
• Establish observability through alerts, dashboards, and runbooks to improve platform reliability.
• Write technical specifications, ADRs, and RFCs to align cross-functional teams.
• Mentor team members and contribute to engineering standards and code reviews.
• Prepare testing infrastructure for AI-assisted development workflows.

Requirements

• 5+ years of software engineering experience.
• Proficiency in backend development using Python, Kotlin, or Java.
• Experience building distributed systems, internal developer tools, or testing infrastructure.
• Ability to manage operational ownership, including incident readiness and system reliability.
• Strong communication skills for producing technical documentation and driving consensus.
• Experience with test automation, mocks, contract testing, and CI/CD platforms.

Skills & tools

• Python
• Kotlin
• Java
• Distributed systems
• Test automation frameworks
• Load testing tools
• CI/CD platforms

Practical notes

• Base pay range: 308,000 zł to 428,000 zł per year.
• Compensation includes equity rewards (Poland 4 grade).
• Benefits include 100% subsidized medical, dental, and vision coverage for employees and dependents.
• Includes monthly stipends for tech, food, and lifestyle expenses.
• Eligible for creative tax benefits subject to local law.
• Includes Away Days for recharging and various learning and development programs.