Top C# Jobs

Design and develop scalable C++ software for endpoint state and control across Windows, macOS, and potentially Linux. Build reliable, multi-process systems that enforce endpoint behavior, manage local state, support IPC, and operate across millions of devices. Responsibilities include implementing features, improving platform performance, writing design documents, defining architecture and IPC contracts, and making technical decisions in an evolving, sparsely documented environment.

Build and scale low-latency ad-serving software handling billions of daily auctions. Responsibilities include developing data- and model-driven features, optimizing algorithms and architectures, reducing cloud costs, extending observability, supporting distributed infrastructure, participating in on-call rotations, and documenting systems and incident procedures.

Designs, develops, tests, deploys, and supports large-scale software for a video advertising platform. Owns feature lifecycles, writes technical specifications and efficient code, integrates software components, documents functionality, and develops quality assurance procedures. Collaborates with product, operations, and engineering teams, provides technical leadership, resolves production issues, researches relevant technologies, and mentors junior engineers. The role requires expertise in C/C++ or Golang, database design, network programming, distributed systems, and large-scale software development.

Develop and test systems-level C++ software that defines and enforces endpoint behavior. Initially, the engineer will own testing infrastructure and coverage for two active projects, then contribute to feature development. The role requires strong C++ fundamentals, automated testing experience, and interest in operating-system concepts such as processes, file systems, services, and APIs. Work includes learning unfamiliar systems, collaborating effectively, and supporting reliable endpoint security and management capabilities.

Develop and architect a cross-platform C++ endpoint patching agent for Windows, macOS, and Linux. Responsibilities include code reviews, mentoring engineers, improving development processes, collaborating across patching teams, and translating product needs into resilient technical designs. The role involves system-level APIs, patch installation and rollback logic, embedded databases, and client-server integration.

Develop and maintain a cross-platform C++ endpoint agent that detects, installs, validates, and rolls back operating system and third-party software patches. Responsibilities include code review, mentoring engineers, improving development processes, collaborating across teams, and translating product needs into technical designs. The role requires system-level development across Windows, macOS, and Linux using modern C++, gRPC, Protocol Buffers, SQLite, and CMake.

Develop modern C++ systems for systematic investing, including low-latency data processing, high-frequency trading execution, quantitative analytics libraries, and machine-learning inference tools. Collaborate with quantitative researchers to build scalable, reliable, and performant production platforms, design distributed data pipelines, evaluate system architectures, and maintain fail-safe live-market trading infrastructure.

Build software, data pipelines, dashboards, and automation for cloud cost visibility, infrastructure efficiency, reliability, engineering productivity, and financial accountability. Analyze workloads and billing data, implement AI- and analytics-enabled forecasting and anomaly detection, develop cloud-native services, and support capacity planning, cost allocation, and optimization. Collaborate with Engineering, Finance, Data, Platform, SRE, Architecture, and Product teams while testing, troubleshooting, documenting, and communicating recommendations and business value.

Develop and maintain sports trading and tools applications and platforms using .NET, C#, and SQL Server. Build scalable, low-latency, highly available software handling high-volume real-time data. Support existing 24/7 trading systems, perform root-cause analysis, collaborate with product owners and testing teams, contribute to solution proposals and estimates, and mentor technical team members. The role will also expand into Golang, React, and Google Cloud Platform.

Design and build data-driven advertising software features, scale distributed applications and infrastructure, optimize algorithms and architectures, reduce cloud costs, and improve observability. Participate in on-call rotations and incident escalation, create technical documentation and playbooks, and collaborate with distributed teams across time zones. The role requires strong software architecture, performance optimization, data modeling, Linux, and compiled-language expertise.

Design and implement high-performance datapath features for load balancing, firewall rules, and Layer 7 protocols. Build scalable networking and security systems using C or C++, data structures, algorithms, and Unix/Linux optimization. Own architectural projects from conception through large-scale deployment while applying advanced knowledge of DNS, HTTP, TCP/IP, and SSL/TLS. Use AI tools to improve engineering workflows and problem-solving.

Design and implement high-performance datapath features for load balancing, firewall rules, and Layer 7 protocols. Build scalable networking and security applications using C or C++, advanced data structures and algorithms, and Unix or Linux systems. Own complex architectural projects from concept through deployment while applying expertise in DNS, HTTP, TCP/IP, and SSL/TLS to enhance global network infrastructure.

Design, develop, and maintain secure, high-quality production code across C#/.NET and Java Spring Boot systems. Produce architecture and design artifacts, apply SDLC and CI/CD practices, use enterprise AI-assisted development tools, and analyze data to improve resiliency and code hygiene. Troubleshoot complex issues and ensure operational stability.

Lead design, implementation, testing, and support of FreeWheel's high-scale video advertising platform. Own feature lifecycle, produce technical specs, write efficient code, integrate components, and maintain documentation. Provide production support, mentor junior engineers, collaborate with product and operations, and drive technical innovation and architectural decisions.

Design, customize, and maintain C++ applications in a Linux environment. Lead releases, collaborate with stakeholders and QA, mentor junior engineers, manage documentation, track performance metrics, and participate in design and peer-programming sessions. May work variable schedules including nights and weekends.

Leads the design, development, modernization, and support of high-performance, low-latency trading software using C++ and FIX. Integrates real-time market data, improves scalability and reliability, oversees testing, debugging, code reviews, deployment automation, documentation, and disaster recovery. Mentors engineering teams, collaborates with traders and analysts, provides technical leadership, and drives adoption of modern technologies and software development practices in a mission-critical trading environment.

The Market Data Engineer will design and implement high-performance market data systems, focusing on trading infrastructure, performance optimization, and system resiliency.

As a Full Stack Engineer, you'll develop online services features using C#, React, and ensure best practices in software development. Collaboration with global teams is key.

The role involves building and supporting production-level trading systems in C++ for credit and rates products, collaborating with traders and quantitative researchers.

Design, develop, and field high-performance Ground Control Station and C2 software using C++/Qt/QML and QGroundControl. Lead architecture and technical direction, mentor engineers, define APIs/ICDs, debug integration/latency issues, support field tests, implement post-mission debrief tools, and ensure interoperability with C2 standards.

Software Engineers at Citadel develop, maintain, and support high-performance trading platforms, focusing on custom software solutions and system stability.

Develop and enhance performance-critical C++ applications for ultra-low latency trading systems, collaborating across teams to analyze and optimize performance.

Responsibilities include developing scalable server-side features, optimizing performance, and collaborating with teams to enhance online services for games.

Develop scalable server-side features, online services, and collaborate with teams. Requires C#, .NET expertise and experience in distributed systems.

Lead design and delivery of ultra-low-latency electronic trading systems (Smart Order Router, Matching Engine, Market Access, Risk Management). Develop and enhance trading strategies, ensure scalability and reliability, conduct code reviews and testing, and collaborate with cross-functional teams following Agile practices.