Top Senior C# Jobs

Leads complex software optimization initiatives from design through implementation and validation. Builds cloud-native services, data pipelines, dashboards, automation, and AI-enabled forecasting solutions. Analyzes cloud costs, resource utilization, reliability, capacity, and engineering productivity while partnering with Engineering, Finance, Product, Data, Platform, and SRE teams. Ensures scalable and secure integrations, testing, observability, financial data quality, and measurable savings. Provides technical leadership and mentorship to junior engineers without direct people-management responsibilities.

Design, develop, optimize, deploy, and maintain high-performance market data and automated trading systems. Process raw market data feeds, implement CME and Cboe exchange protocols, and optimize concurrency, throughput, scalability, and ultra-low-latency performance. Collaborate with traders, quantitative researchers, analysts, and engineers while supporting critical applications, automated testing, peer reviews, and best practices. Coach junior engineers and take ownership of projects from design through maintenance.

Build and optimize low-latency C++ systems for market data processing, exchange connectivity, and order execution. Analyze performance across application, memory, CPU, networking, and operating-system layers. Collaborate with traders, FPGA engineers, and infrastructure teams, while owning production systems through design, testing, deployment, and real-time support.

Design, develop, and maintain high-performance C++ trading platform applications. Partner with traders and quantitative researchers to translate business needs into efficient technical solutions. Lead profiling, performance optimization, testing, code review, and release improvements while owning features from design through production support.

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.

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.

Designs and builds scalable, resilient distributed systems and applications using .NET, C#, microservices, REST APIs, cloud platforms, containers, and DevOps practices. Responsibilities include architecture, coding, code reviews, reusable components, monitoring, continuous delivery, infrastructure as code, cross-functional collaboration, mentoring engineers, and improving engineering processes.

Develop C++ software for a medical and safety equipment technology project. Apply strong object-oriented programming skills, work with PostgreSQL and/or MongoDB, and contribute hands-on development expertise. Experience with Versant DB and embedded systems is beneficial. The role is local to the Boston area and requires at least seven years of C++ development experience.

Lead maintenance and expansion of a flagship Windows client-server accounting product. Design, implement, test, and document features; maintain large legacy C++ codebase while developing in C#/.NET. Collaborate with cross-functional teams, gather user requirements, optimize databases, ensure code quality, and apply finance domain knowledge to deliver reliable accounting software.

Develop and deploy secure payer interoperability solutions using C#/.NET, HL7 FHIR, ASC X12, MongoDB, and Azure. Build APIs, claims and prior authorization workflows, cloud-native data exchange pipelines, and CI/CD deployments. Manage Azure storage, messaging, secrets, and API governance while collaborating with technical and business stakeholders to deliver scalable healthcare integration services.

Develop high-performance C++ services and libraries on Linux for real-time systems integrating AI, hardware interfaces, and sensor data. Optimize CPU, memory, I/O, concurrency, and build performance; debug multithreaded issues; write tests; apply sanitizers and static analysis; and contribute to CI pipelines and developer tooling.

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 and develops a software engineering team while contributing hands-on to enterprise application design, coding, testing, code reviews, production support, and technical decisions. Builds scalable solutions using C#, ASP.NET, SQL Server, and modern web technologies; partners with product and business stakeholders; supports Agile delivery, CI/CD, troubleshooting, root cause analysis, and engineering best practices. The role also includes mentoring engineers, monitoring delivery and operational metrics, and driving continuous improvement.

Provide technical leadership to build, maintain, and optimize core software components/platforms (engine-like) for tech-enabled play using motion, sound, and color detection. Collaborate with firmware and system architects, mentor the team, improve performance on constrained hardware, deliver new experiences, and enhance processes and workflows.

Develop and optimize low-latency C++ software on Linux for IBCS sensor integration and composite track processing. Implement RTI DDS middleware, process and correlate sensor and radar data, support Combat Identification logic, and integrate software with hardware interfaces and battle-management nodes. Collaborate in SAFe/Scrum environments using Jira and Confluence while troubleshooting concurrency, serialization, and network-latency issues.

Develop and optimize high-throughput C++ algorithms for remote sensor data exploitation, image analysis, detection, and tracking. Design software architectures, implement new algorithms, contribute to shared tools, and collaborate within an Agile team. The role requires strong object-oriented programming, database experience, Linux proficiency, multithreading and concurrency skills, data-structure knowledge, and optimization expertise.

Develop and optimize high-throughput C++ algorithms for remote sensor data exploitation, image analysis, detection, and tracking. Design software architectures, contribute to Agile teams and shared tools, and work with databases and Linux systems. The role requires strong object-oriented programming, data structures, concurrency, and performance optimization skills.

Develop and maintain .NET and C# web applications using MVC and IIS on Windows Server. Perform software testing, SQL stored procedure development, SDLC activities, defect tracking, technical documentation, and mentoring of junior personnel. Requires an active TS/SCI clearance with CI polygraph and eligibility for additional clearances.

Develop and maintain high-fidelity, real-time C++ simulation software for SpaceX flight systems and vehicles. Build simulation infrastructure and physics models, prototype designs, improve performance and reliability, and collaborate with engineering teams and simulation users to deliver new capabilities. The role requires strong software development, debugging, optimization, testing, distributed systems, networking, memory management, and physics knowledge.