Software Engineer (C# .Net)

StoneX Group Inc.; Winter Park (FL); On-site; USD 120,000 - 160,000; Full time

Job summary

StoneX Group Inc. is seeking a Staff Software Engineer to join the API & Middleware Group in Winter Park, FL. You will design and operate high‑performance services, contribute to architecture, and drive reliability while collaborating with engineers, tech leads, and QA partners.

You will work with C#, .NET Core, Kafka, and cloud technologies, focusing on scalable middleware and core platform services used globally. The role offers an in‑office environment four days a week in Florida.

Qualifications

• 3+ years of professional experience building distributed systems using C# / .NET
• Strong experience with .NET Core / ASP.NET Core
• Experience with event‑driven architectures and Kafka or similar messaging platforms
• Solid understanding of distributed systems, concurrency, and performance tuning
• Strong SQL experience with relational databases; NoSQL exposure is a plus
• Experience in containerized, cloud‑based environments (Azure preferred)
• Strong ownership mindset and collaboration across teams

Responsibilities

• Contribute across all phases of the software development lifecycle within an Agile team
• Write well‑designed, testable, and efficient code following engineering best practices
• Tackle live production challenges, including troubleshooting and performance issues
• Participate in code reviews (PRs) and contribute as a strong team player
• Work closely with team leads, stakeholders, and partner teams across the organization

Skills

C#

.NET Core

ASP.NET Core

Distributed systems

Kafka

SQL

Azure

Education

Bachelor's degree in Computer Science or related field

Tools

GitHub

Visual Studio

VS Code

Rider

Docker

Kubernetes

TeamCity

Octopus

Job description

Overview

With 5,400+ employees and over 80,000 institutional, commercial, and payments clients, we operate from more than 80 offices spread across six continents. As a Fortune 100, Nasdaq-listed provider, we connect clients to the global markets – focusing on innovation, human connection, and providing world‑class products and services to all types of investors. Whether you want to forge a career connecting our retail clients to potential trading opportunities, or ingrain yourself in the world of institutional investing, StoneX Group is made up of four business segments that offer endless potential for progression and growth.

Corporate

Engage in a deep variety of business-critical activities that keep our company running efficiently. From strategic marketing and financial management to human resources and operational oversight, you’ll have the opportunity to optimize processes and implement game‑changing policies.

Responsibilities

Position Purpose

We are hiring a 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. You will collaborate closely with experienced engineers, tech leads, and QA partners, contributing to architecture, implementation, and operational excellence.

Tech Stack You’ll Work With

• Languages & Frameworks: C#, .NET Core, ASP.NET Core
• Architecture: Microservices, event‑driven systems (Kafka, Redpanda )
• Cloud & Infrastructure: Azure, Kubernetes, Docker, Rancher, TeamCity, Octopus, Grafana
• Databases: Microsoft SQL Server (T‑SQL), PostgreSQL, NoSQL databases
• Tooling: GitHub, Visual Studio, VS Code, Rider, ReSharper
• AI & Developer Tools: Microsoft Copilot, GitHub Copilot, Claude

Primary Duties Will Include

• Contribute across all phases of the software development lifecycle within an Agile team
• Write well‑designed, testable, and efficient code following engineering best practices
• Tackle live production challenges, including troubleshooting and performance issues
• Participate in code reviews (PRs) and contribute as a strong team player
• Work closely with team leads, stakeholders, and partner teams across the organization

Qualifications

• 3+ years of professional experience building distributed systems using C# / .NET
• Strong experience with .NET Core / ASP.NET Core
• Experience working with event‑driven architectures and Kafka or similar messaging platforms
• Solid understanding of distributed systems, concurrency, and performance tuning
• Strong SQL experience with relational databases; NoSQL exposure is a plus
• Experience working in containerized, cloud‑based environments (Azure preferred)
• Strong ownership mindset and ability to collaborate across teams

What will make you stand out

• Work on core platform services used globally
• A strong, collaborative engineering culture
• Exposure to high‑scale, high‑performance systems
• Support for continued technical and professional development

Education

• Bachelor’s degree in computer science, Software Engineering, or equivalent professional experience

Working Environment

• 4 days a week in office