Contractor, Sr Software Engineer in Belfast

Apex Fintech Solutions (Apex) powers innovation and the future of digital wealth management by building tech-forward solutions that help simplify, automate, and facilitate access to financial markets for all. Our robust suite of fintech software enables us to support clients such as Stash, Betterment, SoFi, Webull, and eToro, amongst many others; collectively, Apex powers access to the stock market for over 22+ million end customers.

At Apex, we are changing how the securities industry operates by reinventing the status quo, which was manual, slow, and accessible only by the ultra-wealthy. We're digitizing and democratizing systems so that everyone has an opportunity to invest. When you're at Apex, you drive this change. You're part of a global team with a clear vision: to be the trusted technology that powers the digital economy. Our offices in Austin, Dallas, Chicago, New York, Portland, Belfast, and Manila are home to over 1,000 employees. Together, we’re shaping the future of financial innovation. Embrace change. Solve big. Win together. And be G.R.E.A.T. — grit, results, empathy, accountability, and teamwork — with Apex.

We’re proud to be recognized for the innovative work we do, the purpose-driven nature of our work, and the collaborative culture we’ve created. Here are just a few of the many awards we’ve recently received:

• Best Places to Work 2026, 2025, 2024, 2023 - Presented by BuiltIn
• WealthTech of the Year 2025 - Presented by US FinTech Awards
• The World’s Top 250 Fintech Companies 2024 - Presented by CNBC

Apex Fintech Solutions is seeking an experienced Contractor, Senior Software Engineer to contribute to the ongoing evolution of its cutting-edge Margin product—a critical component of the Apex Ascend platform. This role focuses on designing and delivering key features for real-time buying power calculations along with building highly scalable applications and services. As a Senior Engineer, you will thrive in a fast-paced environment where you will leverage modern cloud-native solutions, contribute to the development of robust backend systems, and work closely with cross-functional teams to influence technology solutions.

Duties/Responsibilities

• Backend Development: Design, develop, deploy, and maintain high-performance backend systems using Java to enhance the functionality and scalability of the Margin product.
• Microservices Engineering: Build and manage containerized microservices using Kubernetes and Docker, ensuring optimal scalability, reliability, and performance.
• Cloud-Native Applications: Develop and optimize infrastructure leveraging Google Cloud Platform and associated technologies such as Google Pub/Sub.
• Distributed Systems: Focus on creating scalable, event-driven systems employing Kafka, RabbitMQ, Redis, and PostgreSQL.
• API Development: Design robust, secure, and efficient gRPC and REST APIs for internal and external system interactions.
• Data Engineering: Design, maintain, and optimize relational databases, with a focus on PostgreSQL/AlloyDB, to ensure efficient data storage, retrieval, and transactional operations within Java-based backend systems.
• Performance Optimization: Tackle complex technical challenges by optimizing system performance, availability, scalability, and maintainability.
• Collaboration & Communication: Collaborate effectively with globally distributed teams, translating technical topics for non-technical stakeholders and aligning architecture strategies across teams.
• Mentorship and Knowledge Sharing: Support junior engineers through mentoring, technical guidance, and sharing best practices to enrich team expertise and project outcomes.
• System Design & Architecture: Contribute to key architectural decisions to ensure solutions are scalable, secure, and well-integrated across multiple teams and systems.

Education and/or Experience

• BA, BS, MS, PhD in Computer Science, Engineering or related technology field (or equivalent work experience) required.
• 5+ years of professional experience in backend software development, with a proven focus on designing, implementing, and maintaining distributed systems and microservices.
• Demonstrated experience guiding projects, working cross-functionally, and mentoring junior engineers, while actively contributing to a collaborative team culture.
• Certifications in Java, Kubernetes, or cloud platforms (e.g., Google Cloud) preferred.

Required Skills/Abilities

• Solid understanding of financial systems, risk modeling, and regulatory compliance to deliver secure and reliable solutions.
• Proficiency in building fault-tolerant systems and high-availability, real-time data processing services.
• Expertise in backend performance tuning and ensuring system scalability and reliability.
• Hands-on experience with DevOps practices, including CI/CD pipelines and deployment automation.
• Deep understanding of securing APIs, backend systems, and cloud-based infrastructures.

Work Environment

This role operates in a hybrid capacity, requiring on-site collaboration two days per week.

Our Rewards

We offer a robust package of employee perks and benefits, including a market-leading salary with an annual bonus, 28 days of annual leave plus 10 Northern Ireland national holidays, a training and development budget, and a pension matched up to 7%. Our benefits also cover private health insurance for medical, dental, and optical care, and life insurance. We emphasize work-life balance with flexible working hours, parental leave, a modern city center office, and a hybrid work schedule that allows for greater flexibility by partially working from home. Additional perks include monthly catered lunches, unlimited drinks and snacks, hackathon events, poker tournaments, and a charitable matching gift program.

EEO Statement

Apex Fintech Solutions is an equal opportunity employer that does not discriminate on the basis of race, color, religion, sex (including pregnancy, sexual orientation, and gender identity), national origin, age, disability, veteran status, marital status, or any other protected characteristic. Our hiring practices ensure that all qualified applicants receive fair consideration without regard to these characteristics.

Disability Statement

Apex Fintech Solutions is committed to creating an inclusive and accessible workplace for all candidates, including those with disabilities. We are dedicated to ensuring equal employment opportunities and providing reasonable accommodations to qualified individuals with disabilities. If you require reasonable accommodations to participate in the application or interview process, please submit your request via the Candidate Accommodation Requests Form. We will work with you to provide the necessary accommodations to ensure your full participation in our hiring process.