Staff Software Engineer - Payment Processing

About the role

Checkout.com enables over 10 billion transactions a year for more than one billion shoppers, powering the payments behind many digital experiences. As a Staff Software Engineer (Payment Processing) based in London, you will set the technical direction for the Gateway, Routing and Payout platforms that handle every payment and payout, from the merchant's API request to the routing decision. The role suits engineers energised by scale and the hard trade-offs involved, such as latency budgets, failure domains and consistency across regions.

Key responsibilities

• Own the architecture of high-throughput, low-latency distributed systems, defining service boundaries, data models and integration patterns.
• Design for resilience from first principles: redundancy, graceful degradation, backpressure, idempotency and recovery.
• Set and defend non-functional requirements: availability targets, latency percentiles, throughput ceilings, data durability and recovery objectives.
• Lead technical decisions end to end, from design review through production rollout, migration and decommissioning.
• Improve observability, alerting, capacity planning, load and chaos testing, and incident response, and close the loop on root causes.
• Raise the engineering bar through design reviews, code review, pairing and mentorship.
• Partner with product, platform and other engineering teams to align multi-team delivery.
• Make pragmatic build-versus-buy and refactor-versus-rewrite calls and explain the trade-offs to engineers and senior leadership.

Required profile

• Significant experience building and operating distributed backend systems in production, with technical leadership across multiple teams.
• Demonstrable experience designing for high throughput and low latency, and a strong intuition for where systems break under load.
• Experience owning production systems on call, with a strong sense of ownership for observability, monitoring and incident response.
• Experience leading complex migrations or re-architectures of live, business-critical systems with no loss of availability or data integrity.
• Excellent communication skills, able to influence without authority and to write clear design documents.

Required skills

• Strong proficiency in either .NET or Java, with production-ready code.
• Deep understanding of resilience patterns: idempotency, retries and backoff, circuit breaking, queueing and backpressure, consistency and failure modes.
• Event-driven and streaming architectures, and relational and non-relational data stores at scale.
• Cloud-based application development (AWS and Azure), containers, orchestration and infrastructure as code.
• Nice to have: payments or financial services experience, multi-region or active-active architectures, and a history of mentoring engineers into senior and staff roles.

What we offer

• Hybrid working model with three days per week in the office.
• A culture of real ownership, fewer blockers and meaningful work from day one.