Job Description

Role Overview:

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.

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.

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.

Responsibilities:

• Build test harnesses that simulate client/exchange and OMS order lifecycle workflows across equities cash and options
• Author automated tests (unit/integration/contract/perf) and grow CI/CD quality gates; make runs deterministic via golden traces/pcaps and time control
• Design performance/latency test rigs (P50/P99.9, jitter, GC/allocator impact) with reproducible results and automatic regressions gates in CI
• Create contract tests and service virtualization (exchange simulators, market-data replayers) to decouple teams and speed releases
• Develop failure-mode/chaos scenarios (disconnects, throttling, slow consumers, sequence resets, clock skew, backpressure)
• Drive cross-repo test architecture/refactors (shared fixtures, contracts, pipelines) to improve coverage and reliability
• Partner with development, SRE, and the trading desk to define and automate end-to-end scenarios that verify system correctness and business workflows

Qualifications:

• Proven ownership mindset: comfortable debugging unfamiliar systems, writing docs, and driving cross-team initiatives
• Expert Python for production-grade automation
• Ability to read/modify C++ test code and hook Python harnesses into C++ components
• Strong Linux and networking fundamentals (TCP/UDP, sockets, pcap/Wireshark)
• CI/CD experience (Jenkins/GitHub Actions, Git, CMake); containerized, reproducible test environments
• Hands-on design of performance/reliability tests (latency, throughput, backpressure) and flaky-test triage
• Excellent communication and documentation skills

Nice to have

• FIX engine experience (QuickFIX or proprietary), exchange simulators, OMS/EMS flows, DMA/algos, drop copy
• Observability for tests (Prometheus/Grafana/Jaeger/Tempo; log correlation)
• Data & infra: kdb+/q, Kafka, low-latency instrumentation
• Rust/Go or FP exposure (Haskell/OCaml); contract testing (Pact) and property-based testing (Hypothesis)
• Prior experience in financial systems or large-scale distributed environments

In accordance with applicable law, the base salary range for this role is $175,000 to $350,000.

In addition, the employee who fills this role will be eligible to participate in a discretionary incentive compensation program, as well as a wide array of benefit programs, such as medical and life insurance, retirement and tax-free savings plans, and access to other healthcare programs.