<p>Job Description</p> <p>Role Overview:</p> <p>The Client Platform technology team builds and evolves the core platform that powers Citadel Securities' client-facing businesses. This platform serves as a critical foundation supporting connectivity, order management, and analytics across multiple asset classes.</p> <p>We are embarking on a multi-year strategic effort to modernize the platform's infrastructure. As a Software Engineer in Test, you'll contribute to this transformation by building Python-first frameworks and C++-adjacent hooks to verify distributed systems correctness, accelerate CI/CD, and protect latency-sensitive releases across equities (cash/options) and beyond.</p> <p>Opportunities may be available from time to time in any location in which the business is based for suitable candidates. If you are interested in a career with Citadel, please share your details and we will contact you if there is a vacancy available.</p> <p>Responsibilities:</p> <ul> <li>Build test harnesses that simulate client/exchange and OMS order lifecycle workflows across equities cash and options </li><li>Author automated tests (unit/integration/contract/perf) and grow CI/CD quality gates; make runs deterministic via golden traces/pcaps and time control </li><li>Design performance/latency test rigs (P50/P99.9, jitter, GC/allocator impact) with reproducible results and automatic regressions gates in CI </li><li>Create contract tests and service virtualization (exchange simulators, market-data replayers) to decouple teams and speed releases </li><li>Develop failure-mode/chaos scenarios (disconnects, throttling, slow consumers, sequence resets, clock skew, backpressure) </li><li>Drive cross-repo test architecture/refactors (shared fixtures, contracts, pipelines) to improve coverage and reliability </li><li>Partner with development, SRE, and the trading desk to define and automate end-to-end scenarios that verify system correctness and business workflows </li></ul> <p>Qualifications:</p> <ul> <li>Proven ownership mindset: comfortable debugging unfamiliar systems, writing docs, and driving cross-team initiatives </li><li>Expert Python for production-grade automation </li><li>Ability to read/modify C++ test code and hook Python harnesses into C++ components </li><li>Strong Linux and networking fundamentals (TCP/UDP, sockets, pcap/Wireshark) </li><li>CI/CD experience (Jenkins/GitHub </li></ul>