Lead Full Stack Engineer (C#/.NET & React)

StoneX Group; Kraków; Hybrid; PLN 120,000 - 150,000; Full time

Job summary

A leading market connection firm in Kraków is seeking a Lead Full Stack Engineer to manage a small team while driving front-end and back-end development. The ideal candidate will have proven leadership experience alongside expertise in .NET and React, with a strong focus on Agile methodologies and cloud services. This is a hybrid role offering an exciting opportunity to influence both people and products.

Benefits

Private parking for employees

Hybrid work model

Career development opportunities

Qualifications

• Proven experience as a Senior or Lead Full Stack Engineer, with demonstrated success leading small teams.
• Strong proficiency in C#/.NET for backend development, including RESTful APIs.
• Hands‑on expertise with React and modern frontend practices.

Responsibilities

• Lead and manage a cross‑functional scrum team of ~5 engineers.
• Contribute production‑ready code while ensuring high standards.
• Act as a technical mentor and drive delivery predictability.

Skills

C#/.NET

React

Azure cloud services

Agile methodologies

CI/CD

Communication

Education

Bachelor’s degree in Engineering or relevant experience

Tools

Docker

Kubernetes

MongoDB

Visual Studio

Job description

Overview

Permanent, full-time, hybrid

Connecting clients to markets – and talent to opportunity.

With 4,300 employees and over 400,000 retail and institutional clients from more than 80 offices spread across five continents, we’re a Fortune-100, Nasdaq-listed provider, connecting 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, The StoneX Group is made up of four segments that offer endless potential for progression and growth.

Business Segment Overview: A Swift-accredited service bureau and member, our Payments division provides NGOs, institutions and non-profits the ability to make a local difference, globally – with transparent pricing across 180+ countries and 140+ currencies.

Technology Ecosystem:

• Languages & Frameworks:
  • Back End: C#, .NET 9, ASP.NET
  • Front End: React, TypeScript/JavaScript (ES6+), HTML5, and CSS/SASS.
• Architecture: Microservices, Event-driven (Kafka, AMQP), CQRS
• Cloud & Infra: Azure, Kubernetes, Docker, Rancher
• Databases: MongoDB, MS SQL Server, PostgreSQL
• Tooling: Git, Visual Studio, VS Code, Rider, Copilot, CI/CD pipelines (Azure DevOps, GitHub)

Responsibilities

Position Purpose: We are seeking a Lead Full Stack Engineer to head the development of Connect, a mission-critical platform enabling trading, pricing, and more for our clients. This role combines hands‑on engineering excellence with team leadership, making it ideal for someone who thrives in a high‑impact environment, enjoys full stack development, and is motivated to grow people as well as products.

As Lead, you will manage a small, agile team of around five engineers, while also contributing directly to the technical direction and codebase. You will be accountable for engineering quality, delivery predictability, and team growth, ensuring that the team operates effectively and efficiently. This is a career‑defining opportunity for an experienced full stack engineer with strong .NET, React, and Azure expertise to step into a leadership role with direct people management.

Primary duties will include:

• Lead and manage a cross‑functional scrum team of ~5 engineers, fostering a culture of collaboration, accountability, and continuous improvement.
• Guide software design and architecture decisions to ensure scalable, robust, and maintainable solutions.
• Own the refinement process – break down complex features into clear, actionable development tasks.
• Contribute production‑ready code while setting high standards in testing, CI/CD, and documentation.
• Act as a technical mentor, supporting professional growth and upskilling within the team.
• Drive delivery predictability and ensure commitments are met, partnering closely with Product and QA engineers.
• Communicate progress, risks, and technical decisions clearly to engineering leadership and stakeholders.
• Stay ahead of emerging technologies, especially within .NET, React, and Azure ecosystems, and recommend improvements to tools and practices.

Qualifications

To land this role you will need:

• Proven experience as a Senior or Lead Full Stack Engineer, with demonstrated success leading small teams.
• Strong proficiency in C#/.NET for backend development, including building and maintaining RESTful APIs.
• Hands‑on expertise with React and modern frontend practices (TypeScript, component‑driven design, state management).
• Experience with Azure cloud services (App Services, Functions, Kubernetes, etc.) and cloud‑native architecture.
• Deep understanding of system architecture, scalable design patterns, and performance optimization across the stack.
• Ability to facilitate refinement sessions and translate product requirements into technically sound, manageable work.
• Strong grounding in CI/CD pipelines, automated testing, and DevOps principles.
• Excellent communicator, able to inspire and guide technical teams while also engaging effectively with non‑technical stakeholders.
• Comfortable working in Agile environments with cross‑functional teams.

Education / Certification Requirements:

• Bachelor’s degree or higher in Engineering (Computer Systems, Software, IT&T, Systems) or relevant experience.

Working environment:

• FTE (UoP).
• Hybrid at ul. Mogilska 35 – we have private parking for employees.

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