Senior Software Engineer, Backend (Comms Core)

About the role

Affirm's Communications team builds and modernizes the highly available platform that delivers billions of customer messages reliably and on time. As a senior backend engineer, you will shape multi-region, multi-tenant infrastructure, APIs and vendor integrations that let product teams communicate with customers at scale. The position is remote in Spain, with an on-call rotation as a requirement.

Key responsibilities

• Own and deliver quarterly technical goals for the Communications area, solving ambiguous problems across messaging infrastructure.
• Design and evolve reliable backend services for high-volume communications, including orchestration, delivery, preferences, templates and observability.
• Collaborate with product management, design, analytics, security and engineering partners, articulating technical constraints and trade-offs.
• Build resilient integrations with external messaging vendors, balancing reliability, latency, cost and compliance.
• Proactively fix issues affecting scalability, developer experience and operational resilience.
• Support service availability by defining SLAs and metrics, improving alerting and incident response, and taking part in on-call.
• Improve design, testing, code review, rollout and operational standards, and share knowledge through writing and tech talks.
• Mentor team members and provide technical direction.

Required profile

• 5+ years of software development or engineering experience, with a deep understanding of system design and architecture.
• Experience building highly available distributed systems and multi-region, multi-tenant platforms with strong isolation, scalability, failure recovery and data consistency.
• Experience integrating with third-party messaging vendors and designing abstractions for different capabilities, rate limits and failure modes.
• Ability to make significant changes in a large codebase safely, with a defined technical plan for major features.
• Strong verbal and written communication skills and ownership of your own growth.

Required skills

• Modern languages such as Python or Kotlin.
• Distributed systems with AWS, MySQL, DynamoDB and Kubernetes.
• AI-assisted development tools, used with sound judgment.

What we offer

• Base pay of EUR 86,000 - 122,000 per year, with equity eligibility.
• Monthly stipends for health, wellness and tech spending, and 100% subsidized medical, dental and vision coverage.
• Flexible spending wallets, away days, learning and development programs, parental benefits and employee resource groups.
• Visa sponsorship available, provided the candidate is based in Spain.