Senior Full Stack Engineer (Java & React)

StoneX Group Inc.; Kraków; Hybrid; PLN 250,000 - 360,000; Full time

Benefits offered by this job

Private parking

B2B contract (12 months)

Job summary

StoneX Group Inc. is seeking a Senior Full Stack Engineer to lead multi-year technical strategy across our React, Node.js, and Java Spring Boot platforms.

You will set architecture standards, resolve complex design challenges, and mentor senior staff within a cloud-based microfrontend and microservice ecosystem on Azure. You will partner with engineering leadership and product executives to align roadmaps with business strategy, evaluate emerging technologies, and drive reliability and security

Qualifications

• University degree in Computer Science or related field.
• Proven track record setting technical direction across multiple engineering teams.
• Experience with cloud architecture and Azure.
• Strong communication with VP- and C-level stakeholders on technical strategy.

Responsibilities

• Define and evolve multi-year technical strategy and architecture across React/Vite, Node.js, and Java Spring Boot.
• Act as final technical escalation point for cross-system design and performance challenges.
• Establish and govern architecture, security, and reliability standards across product teams.
• Mentor Staff and Senior Engineers and shape the technical career ladder.
• Partner with engineering leadership to align roadmaps with business goals.

Skills

JavaScript/TypeScript

React.js

Node.js

Java Spring Boot

REST API design

Distributed systems

Mentoring Staff engineers

Communication with stakeholders

Micro frontends

Education

CS degree or related

Tools

Fastify/Express

Azure DevOps

Azure App Services

Azure Functions

GitHub Copilot

gRPC

Kafka/Redpanda

Job description

Overview

Permanent, full-time, B2B

Connecting 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:

Come join the Nexus project, an ambitious initiative to consolidate all StoneX customer-facing systems into a single application. You’ll be working on a squad within a 150+ global team. Our squad is responsible for delivering multiple features of the user interface for use by tens of thousands of customers.

Technology Ecosystem:

• Back End: Java 21+, Spring Boot, REST APIs, Kafka/Redpanda, gRPC, PostgreSQL, MSSQL, Unit/Integration Testing
• Front End: React.js, Node.js
• Architecture: Micro-services, event-based architecture
• Cloud: CI/CD DevOps, Azure, GitHub Enterprise

Responsibilities

Position Purpose:

We are seeking a Senior Full Stack Engineer to serve as a top-tier technical authority across our engineering organization, shaping multi-year technical strategy for our React, Node.js, and Java Spring Boot platforms. You will define architecture standards spanning multiple product lines, resolve the organization's most complex technical challenges, and grow senior engineering talent. This is a highly influential, largely hands-off-keyboard role focused on technical vision, cross-organizational alignment, and engineering excellence within our cloud-based microfrontend and microservice ecosystem on Azure.

Primary duties will include:

• Define and evolve multi-year technical strategy and architecture standards across React/Vite, Node.js/Fastify, and Java Spring Boot platforms.
• Act as the final technical escalation point for the organization's most complex cross-system design and performance challenges.
• Establish and govern engineering-wide standards for architecture, security, scalability, and reliability across all product teams.
• Mentor and grow Staff and Senior Engineers, and help shape the technical career ladder and promotion criteria.
• Partner directly with senior engineering leadership, principal architects, and product executives to align technical roadmaps with business strategy.
• Lead evaluation and adoption of emerging technologies, driving organization-wide proofs of concept and build-vs-buy decisions.
• Drive resolution of systemic reliability, scalability, and security risks at the platform level, beyond any single team's scope.
• Champion engineering culture, technical documentation standards, and cross-team knowledge sharing at scale.
• Represent engineering in high-stakes technical decisions with external vendors, regulators or enterprise architecture boards where relevant.

Qualifications

To land this role you will need:

• Mastery of JavaScript/TypeScript (ES6+), HTML5, CSS3, and large-scale frontend architecture, including micro frontends.
• Deep, proven expertise in React.js, Node.js, and frameworks like Fastify or Express at enterprise scale.
• Mastery of Java Spring Boot for architecting large-scale, high-availability REST APIs and microservices.
• Demonstrated track record of setting technical direction across multiple engineering organizations or business units.
• Deep expertise in Azure App Services, Azure Functions, Azure DevOps, and enterprise-grade cloud architecture.
• Expert-level understanding of distributed systems, RESTful API design, and enterprise integration patterns.
• History of mentoring Staff-level engineers and influencing organization-wide engineering career frameworks.
• Advanced expertise in database systems (e.g., PostgreSQL, MS SQL Server), including large-scale data architecture decisions.
• Exceptional communication and influencing skills, with experience advising VP- and C-level stakeholders on technical strategy.
• Experience using GitHub Copilot with modern models (e.g., Claude Opus or Sonnet), and shaping organization-wide AI-assisted engineering practices.

What makes you stand out:

• Great knowledge/experience in DevOps and CI/CD

Education / Certification Requirements:

• University qualification in Computer Science, Software Engineering or similar discipline or great GitHub portfolio showcasing your most recent projects.

Working environment:

• Hybrid 4-days in office (we have private parking for employees)
• B2B contract for 12 months