Systems Software Engineer - Security Infrastructure

[Up to c. £225k Comp Package | Office-Led Working - 3 Days Remote Per Month] Role Overview We’re representing a highly successful quantitative research and technology firm operating one of the most sophisticated proprietary engineering environments in the financial markets. The organisation builds a significant proportion of its technology internally, supporting complex research and production workloads where reliability, performance and protection of valuable intellectual property are critical. This team sits at the intersection of software, infrastructure and security, developing bespoke platforms rather than relying heavily on external products. This is fundamentally a systems-focused software engineering role rather than a traditional cyber-security position. You’ll join a small, highly technical team responsible for building and operating proprietary services across backend development, Linux infrastructure, automation, APIs and underlying server hardware. Engineers are expected to investigate problems deeply, own systems throughout their lifecycle and improve or rebuild components where a better engineering approach exists, while gaining exposure to areas including IAM, MFA, cryptography and secure infrastructure... Key Responsibilities Design, build and operate proprietary backend services and internal platforms supporting highly sensitive research, intellectual-property and production workflowsDevelop production-grade services and REST APIs across languages including C#/.NET, Python, Go and Rust, with opportunities to contribute increasingly to Rust-based systemsAutomate Linux server provisioning, configuration and administration using Ansible and CI/CD tooling, including bootstrapping environments from bare-metal infrastructureEngineer concurrent, highly available and fault-tolerant systems where correctness, uptime, observability and predictable behaviour are important operational requirementsTake end-to-end ownership across the software and infrastructure stack, including interaction with physical server hardware and management interfaces such as iLOBuild and maintain systems integrations covering areas such as authentication, MFA, identity functionality, access controls and other internally developed security capabilitiesOwn testing, deployment, monitoring and production troubleshooting, investigating anomalies thoroughly rather than treating operational issues as isolated incidentsAssess existing services and workflows critically, simplifying, replacing or rebuilding components where architectural or engineering improvements would materially strengthen the platform What You’ll Bring… Typically around 4-10 years of professional software engineering experience, ideally working on systems, infrastructure platforms, backend services or other technically demanding production environmentsStrong programming fundamentals in at least one of C#, Java, Python, Go, Rust or C++, with evidence of building substantial production software rather than primarily scripting or configuration workHands-on Linux engineering experience alongside Ansible or comparable infrastructure automation, with confidence working below the application layer and understanding how systems are provisioned and operatedStrong understanding of concurrency, distributed or highly available systems, REST API design and the engineering trade-offs involved in building reliable production servicesExperience owning software through testing, CI/CD, deployment, observability and live production support, with a disciplined approach to diagnosing complex or unexpected system behaviourEvidence of broad technical curiosity and end-to-end ownership, including a willingness to investigate infrastructure, networking, operating-system or hardware-level issues beyond the immediate application boundary(Preferred) Experience building proprietary internal platforms, infrastructure tooling or systems integrations within quantitative finance, trading, technology, research or another high-performance engineering environment(Preferred) Exposure to IAM, MFA, PKI, cryptography, secure infrastructure or similar security concepts, although deep cyber-security or AppSec experience is not required ...