Senior Systems Engineer

Railz

Railz

Software Engineering

London, UK

Posted on May 14, 2026

Position Type :

Full time

Type Of Hire :

Experienced (relevant combo of work and education)

Are you curious, motivated, and forward‑thinking?

At FIS, you’ll work on some of the most complex and impactful challenges in modern banking, helping build next‑generation, AI‑enabled platforms used by financial institutions worldwide. We foster an environment that values ownership, autonomy, and end‑to‑end responsibility, where engineers are encouraged to take initiative, make meaningful technical decisions, and ship solutions directly into production. We believe in open, collaborative, and ownership‑driven teams with a strong focus on real‑world impact.

About the team:

You will build and operate mission‑critical systems responsible for correctness, performance and reliability of high‑volume banking transactions.

What you will be doing:

  • Build transaction processing services with strong correctness guarantees

  • Optimize p95/p99 latency and throughput of critical system hot paths

  • Debug complex system‑level and distributed failures

  • Design and enforce invariants through testing and operational discipline

  • Own observability, on‑call readiness and incident response

  • Use AI‑assisted tools to improve debugging and operational efficiency

What you bring:

  • Strong system-level engineering experience in Go and/or Rust

  • Deep understanding of distributed systems failure modes

  • Performance and concurrency expertise

  • Experience operating production systems at scale

  • Security‑ and reliability‑focused mindset

Added bonus if you have:

  • Low‑level performance profiling experience

  • Financial transaction processing experience

  • Experience designing safe APIs and primitives

  • AI‑driven debugging and observability tooling

What we offer you:

  • A work environment built on collaboration, flexibility and respect

  • Competitive salary and attractive range of benefits designed to help support your lifestyle and wellbeing

  • Varied and challenging work to help you grow your technical skillset

Privacy Statement

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Sourcing Model

Recruitment at FIS works primarily on a direct sourcing model; a relatively small portion of our hiring is through recruitment agencies. FIS does not accept resumes from recruitment agencies which are not on the preferred supplier list and is not responsible for any related fees for resumes submitted to job postings, our employees, or any other part of our company.

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