Senior Backend Engineer

CoinJar is one of the world’s longest-running cryptocurrency exchanges, founded in Melbourne in 2013 and now operating globally. As a fintech company with a decade of operational excellence, we pride ourselves on our resilient, cloud-native infrastructure (with >99.9% uptime!), robust security practices, and a relentless focus on delivering fast, reliable, and delightful experiences for our users—whether they’re crypto newcomers or seasoned traders.

Our culture is all about getting things done, lifelong learning, and genuine empathy for each other and our customers. We value engineers who take ownership, solve real problems, and aren’t afraid to have a little fun along the way. At CoinJar, you’ll find a diverse, friendly, and slightly nerdy team committed to building things that matter (and occasionally sharing a good crypto meme).

This role demands individuals who readily embrace ownership of significant technical challenges and consistently demonstrate the ability to deliver robust and scalable backend solutions. We seek lifelong learners who are not only curious but also possess a strong willingness to expand their skill sets and knowledge base.

• Design, develop, and maintain robust and scalable backend systems for our applications.
• Collaborate with the frontend team to design and implement effective APIs.
• Partner with internal stakeholders to understand and address their needs.
• Participate in project initiation and planning activities.
• Distributed Systems Expertise: Demonstrated experience in designing, building, and maintaining distributed systems, with a strong understanding of microservices architecture and its operational considerations.
• Proven Project Delivery: A verifiable track record of successfully delivering complex software projects from inception to deployment and beyond, showcasing strong ownership and problem-solving abilities.
• AI-Augmented Development Proficiency: Demonstrated experience leveraging AI-assisted development tools (e.g., Claude Code, GitHub Copilot) to accelerate feature design, implementation, and iteration, with a strong understanding of how to effectively integrate these tools into the software development lifecycle.
• Core Ruby Proficiency: Deep and extensive experience in Ruby development is essential. Candidates should possess a thorough understanding of the language's principles, best practices, and relevant frameworks.
• Strict Testing Discipline : Demonstrated commitment to thorough testing practices, including TDD where appropriate, with an understanding of how rigorous test coverage contributes to system stability.
• Security-First Mindset : Understanding of security principles relevant to financial systems, including secure coding practices, data protection and threat awareness.
• Excellent Asynchronous Communication: Exceptional written communication skills are critical for effective collaboration within a distributed team, including clear and concise documentation, technical specifications, and design proposals.

• Hands-on experience working with cloud platforms (e.g., AWS, GCP, Azure) and their associated services, including deployment, scaling, and infrastructure management.
• Strong experience with GraphQL, especially in conjunction with React frontends.
• Prior experience in the cryptocurrency or fintech sectors.
• Familiarity with compliance and regulatory requirements.

• Robust citadel architecture with a 10-year-old Ruby monolith and newer Elixir services.
• Balances stability and agility in a small, lean, and fast-moving engineering environment.
• This is a remote-first team that also holds weekly in-person collaboration sessions.
• Actively explores and embraces state-of-the-art (SOTA) AI and innovation.
• Adherence to superior engineering and security standards is paramount.
• Employees receive the perk of commission-free cryptocurrency trading on our platform.