Top C# Jobs in St. Louis, MO

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.

The C# Developer will design, develop, and support IT solutions using various technologies, ensuring feasibility and leading project initiatives during the software development life cycle.

The Senior Programmer Analyst will develop systems, code and document programs, assist with system design, and improve IT processes and techniques.

The Junior C# Developer will assist in developing system designs, coding, testing, and documenting programs under supervision, while suggesting process improvements.

As a Web Developer, you'll collaborate in a Scrum/Agile team to design and develop web applications using C#, .NET, HTML, and JavaScript, among others.

Design, implement, test, and modernize backend services and integrations (TypeScript/Node.js and C++). Lead large projects, write technical specifications and API contracts, enforce coding standards, coach engineers, and drive legacy-to-modern migrations within online banking and core systems.

Develop and optimize high-throughput, low-latency C++ applications for performance and reliability. Responsibilities include identifying bottlenecks and bugs, refactoring code, conducting peer reviews, developing automated tests, debugging multithreaded systems, and collaborating with QA, Operations, architects, product owners, and cross-functional teams to resolve performance issues.

Contribute to high-performance, real-time applications processing critical financial data. Collaborate with teams, develop clean applications, and maintain testing strategies.

Design, develop, and maintain scalable full-stack enterprise applications using C#, .NET, ASP.NET, and Microsoft Azure. Build RESTful APIs and cloud services, modernize existing systems, troubleshoot production issues, and collaborate with technical and business stakeholders. Participate in architecture, code reviews, testing, deployment, and production support while following secure and maintainable development practices.

Lead and implement observability strategy for Real‑Time Collections, perform hands‑on low‑latency C++ work, embed observability practices across SDLC, define SLIs/SLOs and dashboards, establish GitOps/API-driven observability workflows, and influence platform architecture and reliability.

Evaluate AI coding-agent interactions for usefulness, correctness, engineering judgment, reasoning quality, and developer trust. Provide clear, opinionated feedback, distinguish response-quality levels, and help define standards for excellent interactions with tools such as OpenAI Codex, Claude Code, and Cursor. This contract role requires staff- or principal-level software engineering experience and familiarity with modern AI-assisted development workflows.

Design, build, and maintain scalable full-stack web applications using React, Python, Node.js, and C#. Develop cloud-native AWS solutions with event-driven and serverless architectures, manage relational and NoSQL data stores, write automated tests, maintain infrastructure as code, and contribute to CI/CD pipelines. Collaborate with cross-functional engineering teams on architecture, security, performance, and end-to-end feature delivery in an agile environment.

Develop and maintain end-to-end applications using Python, Node.js, C#, and React. Build scalable backend services, frontend features, APIs, cloud-native AWS solutions, automated tests, infrastructure as code, and CI/CD pipelines. Collaborate with cross-functional engineering teams in an agile, remote environment while contributing to architecture and reliable product delivery for US clients.

Design and implement complex low latency, high throughput software for financial data distribution, conduct testing, and improve software reliability.

The C# / .NET Developer will design and maintain middleware applications, build Shopify integrations, and support a mobile app backend in a remote work environment.

Design and evaluate performance engineering tasks for AI training/evaluation. Optimize runtime, compilers, memory, CPU/GPU and concurrency. Produce documented solutions, evaluate AI-generated code, and build evaluation frameworks and scoring rubrics while collaborating with researchers and SMEs.

Develop user interface components for ArcGIS Pro using C# and WPF, work in an agile team, and design software solutions for raster and imagery processing.

PrivateID seeks a Principal C++ Engineer with at least 10 years of experience to lead complex systems and scale their platform in a remote-first environment.

Build and maintain scalable, cloud-native APIs using .NET. Enhance core platform components, lead architecture and testing discussions, optimize telemetry and performance, collaborate cross-functionally, conduct code reviews, and mentor team members.

You will develop and maintain components of the LLVM based toolchain, collaborating with the community while ensuring platform-specific optimizations and tests.

As a C++ Software Engineer, you will design and develop software solutions, ensuring performance, stability, and quality through testing and collaboration with teams.

Remote backend C# developer to build and optimize a high-load spot-exchange matching engine. Improve performance and API throughput, implement business features, write unit and integration tests, work with .NET Core and PostgreSQL on AWS, and apply multithreading, async, and distributed systems concepts.

Develop and maintain C/C++ software for telecom environments on Linux. Produce software documentation, use git/Gerrit/GitHub/GitLab, perform shell scripting and basic system administration. OpenStack experience is a plus.

Perform civil/structural engineering and design tasks for power plant upgrades and new projects under senior supervision. Assist with calculations, modifications, equipment walkdowns, and design changes to improve plant performance, safety, and reliability. Work involves field and office duties, travel to client sites, and maintaining unescorted nuclear plant access.

Lead technical direction for a major product domain, reduce architectural debt, mentor engineers, standardize AI-agent workflows, and design scalable backend solutions integrating LLMs and cloud services. Drive cross-team RFCs, cookbook standards, and adopt agentic AI tooling while balancing security, quality, and delivery.