Senior Backend Engineer

Senior Backend Engineer (Ruby) Role type - Permanent Location - Holborn, London (Hybrid) About Zuno Zuno is the cutting-edge technology platform powering the success of home heating and cooling experts, BOXT. Zuno is scaling for significant growth by continually developing its proprietary tech stack to empower both our installers and the homeowners of brands such as E.ON Next and BOXT. Our platform manages the end-to-end installation process for a complete range of modern home energy solutions - from high-efficiency boilers and air conditioning to heat pumps, solar panels, battery storage, and EV chargers. No matter what we are installing, our ethos remains the same: we use technology to make buying, installing and maintaining products an efficient, stress-free, seamless experience for our users. Every year millions of people come to our site to get a fixed-price quote. We’ve installed over 200,000 products so far, while establishing a network of more than 15,000 professionally accredited installers. Our revolutionary platform is market-leading. And we’ve got the supporters to shout about it. We’re backed by Brookfield and work in partnership with some of the world’s most famous household names including Tesla and Eon. The role As a Senior Backend Engineer, you will be acting as a technical anchor within the team, defining the architectural direction of our server-side logic and ensuring the scalability of our data models. You will partner with Product Managers to shape the roadmap and ensure technical feasibility from the outset. In this role, you will be responsible for designing and optimising high-performance APIs and complex business logic using Ruby on Rails. While your focus is backend, you will work closely with frontend engineers to define API contracts and ensure seamless integration with our Next.js frontend. You'll also contribute to keeping the quality of the code top-notch by reviewing your teammates' code and mentoring junior engineers. Key responsibilities Core Backend Architecture: Design, build, and maintain robust, scalable, and secure backend features using Ruby on Rails, ensuring business logic is encapsulated and efficientAPI Strategy: Architect and document performant RESTful APIs, acting as the bridge between server-side logic and the React/Next.js frontend teamsTechnical Leadership: Lead technical discussions on system design, database schema planning, and the decoupling of monolithic services where necessaryPerformance & Scalability: Proactively identify and resolve performance bottlenecks, focusing on SQL query optimisation, caching strategies (Redis), and background job management (Sidekiq/Solid Queue)High-Quality Engineering: Write clean, maintainable, and efficient code that adheres to best practices (including Test-Driven Development and Continuous Delivery)Feature Ownership: Take ownership of complex backend features from concept to deployment; assisting the Product Team in scoping requirements and managing technical debtDriving Engineering Culture: Act as a catalyst for technical excellence by evolving our backend engineering standards (OOAD, SOLID principles) and internal processes. You will proactively identify and resolve bottlenecks, whether in code, deployment, or communication, advocating for the changes needed to make the backend team faster, safer, and more efficient.Mentorship: Actively mentor junior and mid-level engineers, fostering a culture of continuous learning and technical excellenceSystem Reliability: Debug and resolve complex issues in production, ensuring high availability and data integrity for our installer and customer platformsContinuous Improvement: Stay up-to-date with the Ruby on Rails ecosystem and emerging backend technologies, bringing fresh ideas to the team to improve our infrastructure Skills 5+ years of professional experience in backend developmentDeep expertise in Ruby and the Ruby on Rails framework, including a strong understanding of metaprogramming and the Rails internal architectureProven ability to design complex, normalised database schemas and write performant SQL (PostgreSQL focus), with a keen eye for avoiding and resolving N+1 queries and lock contentionA firm grasp of Object-Oriented Analysis and Design (OOAD), design patterns, and software engineering best practicesExperience designing and maintaining versioned, documented RESTful APIsExperience writing comprehensive automated tests using RSpec, including integration and request specsExperience working within Agile development methodologiesProficiency with version control systems, particularly Git, and modern workflows (Pull Requests, Code Reviews)Strong problem-solving skills, with a focus on writing simple, clean, and efficient codeNatural tendency to identify internal pain points and the initiative to propose and implement technical or procedural improvementsExcellent communication skills, with the ability to explain complex backend concepts to frontend developers and non-technical stakeholders Beneficial Skills Advanced DevOps experience (Infrastructure as Code, AWS, Kubernetes, Docker)Experience with React and Next.js (ability to read frontend code to understand how it consumes your APIs)Experience with TypeScriptKnowledge of Site Reliability Engineering (SRE) practices and monitoring tools (New Relic)Experience scaling applications using background processing tools (Sidekiq) Benefits 30 days annual leave + bank holidaysPrivate medical cover with Aviva*4 x salary Death in Service cover with Zurich*Paid 6 months maternity pay after a year of servicePaid paternity pay after a year of service£1000 annual training budget*Salary sacrifice pension matched up to 6%Flexible working times and locationCompany MacBook Pro & accessoriesTeam lunches, team eventsAfter probationary period At Zuno Tech, we believe diverse perspectives make us better at what we do. We’re committed to fostering an inclusive, welcoming environment where everyone, regardless of background, identity, or experience, feels valued and supported. If you’re excited about this role but don’t meet every qualification, we encourage you to apply. Your unique perspective could be exactly what we need to grow and thrive