Back End Engineer

Blockchain is connecting the world to the future of finance. As the most trusted and fastest-growing global crypto company, it helps millions of people worldwide safely access cryptocurrency. Since its inception in 2011, Blockchain has earned the trust of over 90 million wallet holders and more than 40 million verified users, facilitating over $1 trillion in crypto transactions.

As a Back-End Engineer on our Cryptocurrency Trading Platform, you will build the backend services that power our internal and external trading products — from order management and market data processing to the REST APIs and WebSocket streams that serve our web and mobile clients. You'll work closely with product, engineering, and trading teams, and contribute to our culture of engineering excellence. The role is based in London and the team is international.

WHAT YOU WILL DO

• Design, build, and operate backend services in Kotlin and Python that power our trading products, from core trading workflows to client-facing APIs.
• Develop and improve services for order management, market data processing, and trade lifecycle handling in a real-time, high-volume environment.
• Build and maintain REST APIs and WebSocket streams that deliver real-time prices, order updates, and account data.
• Collaborate with cross-functional teams — product, frontend, trading — to adapt the platform quickly to new features and market conditions.
• Ensure high availability, reliability, and scalability of trading services, with a sharp focus on latency, observability, and testing.
• Contribute to architecture discussions and technical decisions, writing clean, maintainable code and sharing knowledge across the team.

WHAT YOU WILL NEED

• Professional experience building backend services, ideally in Kotlin and/or Python.
• Solid experience designing and building backend services and REST APIs; experience with WebSockets or other real-time streaming protocols such as NATS/JETSREAM is a plus.
• Working knowledge of SQL and experience integrating with multiple internal or third-party services.
• An understanding of performance fundamentals — identifying bottlenecks, managing latency, and building systems that stay responsive under load; experience with real-time or event-driven systems is a plus.
• Strong problem-solving skills and clear communication with both technical and non-technical colleagues.
• Curiosity and enthusiasm for learning new technologies; interest in financial markets or crypto is a plus, not a requirement.
• Familiarity with Docker/Kubernetes and cloud environments (AWS) is a plus.