Top C# Jobs in Philadelphia, PA

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.

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.

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.

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.

Architects, develops, and maintains high-performance C++ applications with advanced memory management and multithreaded architectures. Owns critical system components, build systems, CI/CD pipelines, containerization, debugging, profiling, and performance tuning. Leads code reviews, technical planning, and system design while mentoring engineers. Works in Linux environments with Python, shell scripting, SQL, and Git, and collaborates across teams to improve reliability, scalability, and technical growth.

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.

Lead the architecture, design, and implementation of core MarkLogic database features using C++. Build scalable, fault-tolerant distributed systems; optimize performance; debug complex server-side issues; and mentor engineers. Collaborate with product, development, QA, and documentation teams to deliver secure, high-quality database capabilities involving search, security, language runtimes, JavaScript integration, scalability, and reliability.

Develop and maintain backend services and RESTful APIs using C# and .NET. Design and optimize MySQL schemas and queries, troubleshoot production and staging issues, improve performance and scalability, document architecture, and uphold code quality and security. Collaborate with cross-functional teams in a fully remote environment while contributing to development best practices and continuous improvement.

Develop and enhance software in C++ on Linux, create analytical tools for financial data, and collaborate with research analysts.

Develop software and enhance systems in C++ on Linux, while collaborating with analysts and engineers to create data processing tools.

Develop and maintain infrastructure for market data feeds, focusing on performance and latency in a real-time financial environment.

Leads instrumentation and controls engineering design for small to medium projects, including programming, planning, detailed design, construction documentation, and administration. Develops automation control systems with controllers, HMIs, workstations, and servers; manages discipline budgets, coordinates clients and project partners, leads quality reviews, supports proposals, performs field surveys, writes specifications, and mentors junior engineers.

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.

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.

Design, implement, and maintain high-quality C++ (C++17/20) robotics software. Improve build systems (CMake), configure GitLab CI/CD, maintain Linux development environments, write unit/integration tests, profile and optimize performance, collaborate with controls and hardware engineers, participate in code reviews, and support tooling and CI infrastructure to keep development fast and reliable.

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.

Seeking a Senior iOS Developer to design and build high-performance iOS applications. Requires 5+ years in iOS development with Swift and Objective-C, experience with REST services, and skills in data persistence frameworks. Occasional travel may be needed.

Develop and maintain C++ UI applications on UNIX; apply OOP design, database knowledge, and security concepts (SSO, XSS, SQL injection). Lead small teams, work flexible hours, and communicate technical solutions.

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.