Flow Traders is transforming its institutional trading platform across Equities, ETFs, Fixed Income, and Crypto. As part of OTCTECH, you will work directly with traders, quants, Operations, Risk, and Compliance to design and deliver a new OTC Trading Engine, automate operational workflows, and modernise existing applications into reliable, maintainable systems. We are looking for a Senior Software Engineer who can take ownership of complex problems from discovery through production. You will need to understand how trading activities and data flow across systems, define clear technical boundaries, make sound architectural decisions, and build solutions that perform reliably in a demanding environment. This role combines greenfield platform development with the opportunity to understand and evolve an established technology estate. It is grounded in strong engineering fundamentals, with quality, correctness, operational resilience, and clear technical judgment at its foundation.   What you will do Understand the Trading Domain • Work directly with traders, quants, Operations, Risk, and Compliance to understand requirements and how trading workflows operate in practice. • Trace business processes and data flows across pre-trade research, execution, post-trade processing, risk, and compliance. • Identify opportunities to improve resilience, consistency, automation, and operational efficiency. • Build a shared understanding of system responsibilities, dependencies, and operational considerations. • Design and Modernise the Platform Help design and deliver a new OTC Trading Engine spanning Equities, ETFs, Fixed Income, and Crypto. • Define appropriate service boundaries, data models, interfaces, and event flows. • Modernise existing applications where new business or engineering requirements create opportunities for improvement. • Make and document architectural decisions, balancing performance, reliability, simplicity, and delivery speed. • Design greenfield services and platforms that can be operated and evolved safely over time. Build Reliable Trading Systems • Develop high-performance services, data pipelines, and integrations across Java, C++, and Python environments. • Build event-driven systems using messaging and pub/sub patterns. • Engineer for production from the outset, including testing, observability, failure handling, and operational support. • Embed monitoring, root-cause analysis, and recovery mechanisms so issues are identified and resolved quickly. • Take ownership of delivery from design and implementation through deployment and production operation.   What you need to succeed • Strong experience building and operating distributed backend systems in production • Expert in Java or C++, with working knowledge of Python • Strong understanding of distributed systems, concurrency, and scalable system design • Experience with event-driven architectures and messaging platforms such as Kafka • Proven track record building high-performance, low-latency systems • Ability to translate complex business requirements into robust technical solutions • Ownership mindset with strong stakeholder management and communication skills • Experience with modern engineering practices including testing, code reviews, observability, and automation • Comfortable leveraging AI tools to improve productivity while maintaining quality and accountability. Nice to have • Experience in trading, capital markets, or financial services • Exposure to Google Cloud Platform (GCP) • Experience with Kubernetes, Docker, and cloud-native technologies • Knowledge of BigQuery or large-scale data platforms • Experience working in low-latency, high-throughput environments What we offer At Flow Traders, we create the conditions for hard‑working, high‑performing people to do their best work. From a thorough onboarding and ongoing access to Flow Academy, to latest technology and a collaborative, non‑hierarchical culture, we give you the tools, ownership, and support to move fast and drive outcomes. We keep a close‑knit, small‑company feel while offering competitive salary, annual discretionary profit share, and comprehensive benefits, so talent can grow here, and stay here. See our benefits below: • Flow Academy and opportunities to attend domain-related conferences • Daily catered lunch, great coffee, and a fully stocked kitchen and snack bar • In-house Bar and Lounge with arcade, table tennis, billiards, and game consoles • Company boat • In-house gym and sessions with our nutritionist or personal trainer • Bi-weekly massages • Annual company trip and a variety of events throughout the year, such as the New Years Event • Global rotations across our offices worldwide • and more   This role may require participation in an on-call rotation outside normal business hours and on applicable National Holidays. Employees on call must remain available to respond to urgent matters necessary to ensure business continuity or 24/7 coverage of trading activities. On-call duties, scheduling, and compensation are governed by the applicable company policy, arrangements, and Dutch labour-law requirements. Flow Traders does not accept unsolicited resumes from any professional staffing or search firms. All resumes, and any other information identifying potential candidates, submitted to any employee at Flow Traders via-email, the Internet or directly without a valid and signed search agreement will be deemed free to contact by Flow Traders without any restrictions and no placement fee of any kind will be paid in the event the candidate is hired by Flow Traders