Software Engineer III, Backend - Protection

An Introduction to Primer

Primer is the unified infrastructure for global payments. We give finance and payments teams the visibility and control to reduce complexity, improve performance, and capture more revenue — all from a single platform.

Which team will you be joining?

We play a key role in helping merchants handle disputes and prevent fraud. The Protection team owns the risk management suite that surfaces these threats, and helps merchants build automation to handle them at scale.

What will you be doing?

• Own individual features end-to-end within the dispute automation buildout — deadline tracking, evidence collection, response templates by reason code
• Extend dispute lifecycle coverage to new PSPs, working from the existing pattern across the first five
• Build components of the native rules and signals engine — velocity rules, blocklists, device fingerprinting
• Contribute to the fraud vendor integration work (Riskified, Forter, Signifyd, Sift), improving how merchants compare and switch between providers
• Write RFCs and ADRs for the pieces you own, working mostly independently with light input from senior engineers
• Work closely with Product and your EM to turn a scoped piece of merchant pain into shipped automation
• Move across backend and, where needed, support the development of a new frontend Dispute Management dashboard

What we're looking for

• Recent experience shipping production-ready software from scoping through to rollout—backend or full-stack—independently
• Comfortable writing RFCs and making architecture calls on your own projects with minimal senior oversight
• Comfortable transitioning into Python without prior experience
• Solid instincts on testing, observability, and security

Nice to have, not required

• Exposure to card scheme rules, chargeback workflows, or fraud vendor integrations
• Experience with webhook-based event systems, rules engines, or orchestration platforms

What you should know

• This team is new enough that some structure—on-call rotas, tooling, conventions—you'll be building it alongside doing the actual work
• Real ambiguity in the early days: you will be the one deciding what "good" looks like before anyone else has an opinion
• A handful of people today, so your individual output is highly visible

Interview Process

• An initial intro call with a Talent Partner
• An interview with the Hiring Manager
• Challenge Stage — Contextualised to the role
• A final, values-alignment interview