Lead .NET Engineer with Agentic Development at StoneX · Krakow

Overview

Permanent, full-time, hybrid

C onnecting clients to markets – and talent to opportunity.

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.

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.

Responsibilities

Position Purpose: We are seeking a Lead .NET Engineer to design, build, and lead the evolution of high-impact backend systems powering business-critical applications across StoneX Payments.

This role is ideal for a highly experienced backend engineer who:

• Thrives on end-to-end ownership across the SDLC.
• Influences technical direction across multiple squads.
• Leads complex initiatives without formal people management.
• Actively advances agentic development practices within engineering.

You will operate as a technical authority within your domain — shaping backend architecture, raising engineering standards, and enabling teams to safely leverage AI-augmented development in a regulated financial environment.

Key Responsibilities will include:

Backend Architecture & System Design

• Own the technical direction of FX Payments within your domain.
• Lead design and evolution of scalable, maintainable fullstack solutions using:
  • C# / .NET,
  • React / TypeScript,
  • Azure cloud-native services
• Contribute to domain architecture strategy and ensure alignment with platform principles.
• Lead complex technical initiatives spanning multiple squads.
• Drive improvements in system performance, reliability, observability, and data integrity.
• Champion clean architecture, modular design, and maintainable service boundaries.
• Ensure architectural decisions support performance, resiliency, observability, and regulatory compliance.
• Conduct structured design reviews and maintain architectural documentation and ADRs.
• Drive modernization of legacy components toward modular, testable, cloud-ready patterns.

You are expected to influence architecture beyond a single squad and elevate backend engineering standards across the domain.

End-to-End Delivery & Technical Execution

• Participate across the full SDLC — from story refinement and design through implementation, deployment, and production support.
• Write high-quality, testable, production-grade backend code.
• Lead technical breakdown of large features and complex initiatives.
• Ensure strong automated testing (unit, integration, contract, e2e tests) and CI/CD hygiene.
• Drive technical risk identification and mitigation early in the lifecycle.
• Support incident resolution and root cause analysis in production systems.
• Partner closely with Product, QA and Architecture stakeholders.

3. Technical Leadership Without Direct Management

• Serve as a senior technical reference point for backend engineers.
• Drive effective refinement — translating product requirements into clear, technically sound work items.
• Maintain predictable delivery through disciplined planning, risk management, and dependency tracking.
• Own and drive cross-team initiatives that improve delivery process.
• Conduct rigorous code reviews and architectural deep dives.
• Facilitate architecture discussions and influence technical decisions across squads.
• Contribute to internal standards, documentation, and reusable backend patterns.
• Mentor engineers in:
  • Backend design patterns
  • System design
  • Clean coding standards
  • Cloud-native patterns
  • Distributed systems principles
  • Responsible use of agentic tooling

This role leads through influence, expertise, and technical credibility rather than formal people management.

Qualifications

To land this role you will need:

Core Backend Engineering

• 8+ years of professional software engineering experience with strong backend focus.
• Deep expertise in C# and .NET.
• Extensive experience with microservices, event-driven architectures, messaging, and distributed systems.
• Solid understanding of clean architecture, SOLID principles, and scalable design patterns.
• Experience with relational and/or NoSQL databases.
• Strong grounding in CI/CD, version control (Git), and cloud-native development.
• Extensive Azure cloud experience (App Services, Functions, Kubernetes, containerized workloads).
• Familiarity with infrastructure-as-code and observability tooling.
• Knowledge of frontend development, frameworks (in particular React) and tooling.

Agentic Development Capabilities

• Hands-on experience using AI-assisted development tools (e.g., Claude Code, GitHub Copilot, Copilot Workspace, or equivalent).
• Ability to evaluate and validate AI-generated backend code for correctness, maintainability, and security.
• Understanding of how architecture quality, modularity, and test coverage influence agent effectiveness.
• Experience improving legacy systems in ways that increase automation and agent compatibility.
• Pragmatic mindset balancing acceleration with governance and financial system rigor.

Collaboration & Influence

• Strong cross-functional collaboration skills with Product, QA, Frontend engineers, and DevOps.
• Strong stakeholder management.
• Strong facilitation skills for refinement and technical discussions.
• Experience leading small engineering teams.
• Experience leading technical initiatives without direct people management.
• Clear communicator capable of articulating architectural trade-offs and technical risks.
• Comfortable operating in Agile, distributed environments.

Why Join Us?

• Work on meaningful backend systems with real business impact.
• Influence architecture and engineering standards across teams.
• Help shape the adoption of agentic development in a modernizing payments platform.
• Operate at the intersection of distributed systems, cloud architecture, and AI-augmented engineering.
• Clear progression towards Principal Engineer technical role.

Education / Certification Requirements:

• min. Bachelor’s degree in information technology or software engineering discipline.

Working environment:

• Hybrid 4-days in office (we have private parking for employees)
• FTE (UoP) type of contract

#LI-DK1