Top C# Jobs

Software Engineers at Citadel develop software solutions for trading platforms, optimizing performance and functionality, and support trading activities.

Design, develop, integrate, test, deploy, and maintain high-performance DNS resolution software in a collaborative Agile environment. The role involves systems programming in C, C++, or Rust; networking and routing protocols; automated testing; CI/CD; infrastructure automation; vulnerability management; troubleshooting; and Linux-based distributed system operations. Engineers own features from design through delivery, contribute to technical leadership and best practices, and collaborate closely with team members.

Design, develop, and support reusable components, interactions, frameworks and SDKs for Spectacles AR glasses and SnapOS. Contribute to OS components, participate in code and design reviews, and collaborate with design, engineering, and product teams to launch performant, test-covered features.

Designs, develops, tests, and troubleshoots secure, stable .NET applications. Writes high-quality C# code, works across the SDLC, uses CI/CD and AI-assisted dev tools, and collaborates within agile teams to ensure operational stability.

Develops and maintains control-plane software for Layer 2 networking and switching systems. Responsibilities include requirements analysis, software design, C/C++ implementation, unit and integration testing, test automation, performance optimization, troubleshooting, root-cause analysis, and collaboration with architects and distributed teams. The role also contributes to technical specifications, customer issue resolution, standards, white papers, and patents.

Develop and maintain C/C++ software for mission-critical C4I, radar surveillance, and ISR systems. Responsibilities include sensor integration, radar tracking, sensor fusion, data correlation, real-time displays, troubleshooting, performance optimization, deployments, testing, documentation, and collaboration with government stakeholders and AI/ML teams. The role requires expertise in real-time and multithreaded programming, Linux environments, networked data, legacy codebases, and tracking algorithms.

Design and develop low latency, high-performance trading systems. Optimize code and solutions for hardware efficiency, ensuring seamless application integration.

Designs, implements, and tests firmware and software systems; analyzes hardware-software interactions; collaborates with hardware engineers; maintains design and test documentation; and mentors associate engineers and technicians. The role involves graphical user interface applications, embedded Linux development, embedded firmware, object-oriented programming, and real-time systems. Preferred knowledge includes industrial controls, electric power systems, communications protocols, circuitry, signal processing, and project management.

Develop and optimize high-performance C++ numerical simulations for hydrology and water resources applications. Maintain and enhance Windows desktop software and cloud-based SaaS products, addressing computational efficiency, numerical stability, and large-scale data challenges. Collaborate with water resource engineers to translate scientific concepts into software, while contributing to architecture, code reviews, documentation, unit testing, debugging, and continuous improvement.

Develop and optimize a Windows desktop application featuring geospatial rendering, GIS visualization, and hydraulic model editing. Responsibilities include maintaining the rendering engine, implementing 2D/3D DirectX pipelines, developing computational geometry algorithms, integrating geospatial formats and coordinate systems, testing, documentation, code reviews, and mentoring junior engineers. The role collaborates with technical subject-matter experts to enhance the platform and support water resources engineering applications.

Lead end-to-end development of secure, scalable web applications and data solutions supporting clinical trial operations. Design frontend and backend components using C#/.NET, Angular, AWS, and relational or non-relational databases. Guide architecture, testing, deployment, CI/CD, security, cloud optimization, and regulatory compliance. Mentor developers, oversee technical delivery, troubleshoot complex issues, and lead migration and modernization of on-premises applications to AWS.

Develop and maintain production front-end trading software using C#, WPF, and MVVM. Responsibilities include creating prototypes, reusable controls, themes, style dictionaries, interactive user experiences, and production-ready components. Collaborate across teams, apply design patterns and development best practices, and test and resolve product issues. The role requires onsite work in Great Neck, Long Island, New York.

Develop high-performance backend applications and distributed-system infrastructure that collect and process large volumes of data. Own features from planning and design through development, testing, and delivery. Collaborate within Scrum/Agile teams and across internal stakeholders while writing clear, reusable, testable code. The role focuses on enterprise backend development, multithreading, network protocols, and security-focused software protecting enterprise data.

Design, implement, operate, and optimize ultra-low-latency electronic trading systems on Linux. Responsibilities include building distributed real-time systems, analyzing packet captures and core dumps, troubleshooting performance, using profiling and benchmarking tools, and optimizing networking, concurrency, throughput, and reliability. The role spans architecture through live production debugging and involves collaboration with developers, traders, and operations teams.

Develop and maintain high-quality features for insurance software, perform unit and integration testing, debug across OS/DB/app/network layers, fix production issues, and collaborate with peers. Own technical growth, follow industry/open-source trends, and contribute to UI design and Agile development processes.

Design and develop C/C++ software for complex distributed and high-performance computing systems. Build multithreaded and multiprocess applications on Linux, use Python scripting, work with networking stacks, and troubleshoot HPC systems. Preferred experience includes cloud infrastructure, containerization, Linux kernel configuration, network infrastructure, device drivers, and real-time systems. The role requires strong problem-solving and communication skills.

Design and implement high-performance GPU-accelerated software using C++ and CUDA. Develop CUDA kernels for signal and image processing, profile and optimize GPU applications, integrate with hardware (FPGAs, SoCs), collaborate with cross-functional teams, and apply DevSecOps/CI-CD practices to deliver production-quality defense systems.

Build and maintain C#/.NET backend services on Azure that ingest and process telemetry from distributed energy devices. Develop APIs, storage, dashboards, factory-floor applications, automated tests, and CI/CD pipelines. Troubleshoot systems end to end using logs, metrics, and traces, improve observability, document designs, and collaborate with software, hardware, data science, manufacturing, and field teams.

Build and maintain C#/.NET backend services on Azure that ingest and process telemetry from distributed energy devices. Develop APIs, storage, dashboards, and internal applications; troubleshoot systems using logs, metrics, and traces; write automated tests; support CI/CD and observability; and document designs for customer security reviews. Collaborate with software, hardware, data science, manufacturing, and field teams in a hybrid Houston environment.

Develop C++ checkers and defect-fix algorithms for a static code analysis tool. Contribute to core source-code analysis and transformation algorithms, participate in daily Scrum meetings, and help advance AI-enabled software quality products.

The Software Engineer II will design, develop, and maintain secure software solutions, focusing on smart card personalization products and HSM firmware development, while ensuring alignment with security standards.

Design, own, and optimize low-latency trading infrastructure supporting real-time data processing, order execution, market data, and strategy implementation. Build fault-tolerant systems, execution logic, venue gateways, test harnesses, and data-analysis pipelines. Partner with quantitative researchers and traders while making architectural decisions, applying modern C++ practices, and supporting systems from design through production. The role requires onsite collaboration four days per week.

Build and integrate cloud-based backend microservices for multiplayer games. Develop scalable services, networked features, and live game functionality; integrate platform and console services; support certification; troubleshoot PC and console issues; collaborate with designers, partner studios, and external programmers; and create maintainable software and design documentation.

Develop C and C++ applications for Linux, Unix, and Windows environments, including real-time embedded systems. Install and support hardware, servers, and rack components while working with x86 and ARM processors. Apply object-oriented development principles, meet project timelines, produce high-quality software, document work, communicate effectively, and collaborate with peers in a changing environment.

Design and develop massively parallel distributed database kernels for real-time analytics at terabyte and petabyte scale. Responsibilities include low-level C++ development, MPP query execution, SIMD and hardware optimization, distributed communication using MPI and RDMA technologies, database internals, vector indexing, in-database machine learning, performance tuning, architecture reviews, mentoring, and resolving scalability issues.