Senior Software Engineer (C#)
Listed on StoneX Group’s official careers site. Posted October 12, 2026. Check that it is still open and apply there.
Apply on StoneX Group’s careers site →Job description
Overview
About the Role We are hiring a Senior Staff Software Engineer to join the API & Middleware Group, a central platform team responsible for building scalable APIs, middleware services, and event-driven systems used across the organization. This role focuses on designing and operating high-performance, low-latency services that run under significant load and strict reliability requirements. You will work on distributed, data-intensive systems that enable system-to-system integration and platform-level capabilities.
This role is ideal for an experienced .NET engineer who thrives on ownership, stays up to date with the newest .NET technologies, and brings deep expertise to high-load, low-latency systems. You will collaborate closely with experienced engineers, tech leads, and QA partners, contributing to architecture, implementation, and operational excellence.
Responsibilities
Primary Duties will include
- Design and develop low-latency solutions using the latest .NET technologies; build performant, scalable backend services from scratch or improve existing ones
- Write well-designed, testable, and efficient code; ensure designs are in compliance with specifications Tackle live production challenges, including troubleshooting and performance issues Do proof of concepts to test out various ideas and technologies
- Support continuous improvement by investigating alternatives and technologies and presenting these for architectural review
- Mentor and support engineers with technical direction and best practices
- Participate in code reviews (PRs), design sessions, and agile ceremonies; contribute as a strong team player
- Work closely with team leads, stakeholders, and other teams across the company Continuously explore and evaluate new technologies that could enhance the platform Tech Stack You’ll Work With Languages & Frameworks: C#, .NET Core, ASP.
NET Core Architecture
Microservices, event-driven systems (Kafka, Redpanda), CQRS Cloud & Infrastructure: Azure, Kubernetes, Docker, Rancher, TeamCity, Octopus, Grafana Databases: MS SQL Server (T-SQL), NoSQL, PostgreSQL Tooling: GitHub, Visual Studio, VS Code, Rider, ReSharper AI & Developer Tools: MS Copilot, GitHub Copilot, Claude Primary Duties will include
- Work closely with team leads, stakeholders, and other teams across the company Continuously explore and evaluate new technologies that could enhance the platform Qualifications
What We’re Looking For
- Minimum 5+ years’ experience building global enterprise-level systems
- Knowledge of financial markets or a strong desire to learn
- Proven hands-on experience designing and developing enterprise applications using C# / .NET Core / .NET 8 or higher
- Solid grasp of .NET Core APIs, high-load systems, multithreading, and performance tuning Experience developing distributed systems using microservice architecture (event-based) Experience with messaging systems like Redpanda and Kafka Hands-on experience with Kubernetes and containerization (Docker); experience working on cloud platforms (Azure preferred)
- Excellent knowledge of relational databases (SQL) and NoSQL databases
- Strong communication skills and the ability to collaborate across teams A growth mindset and eagerness to stay current with industry trends Education BS/MS degree in Computer Science, Engineering, or a related subject
What We Offer
Work on mission-critical systems used globally Ownership, and room to grow technically and personally A strong, collaborative engineering culture with talented peers Hybrid work flexibility Support for continued technical and professional development
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