Senior Backend Engineer

Senior Backend Engineer We’re building the next generation of employee benefits infrastructure. At Happl, we help global teams design, manage, and scale benefits that actually work for their people by using AI, across flex allowances, benefits, insurance, recognition, and wellbeing, all in one intelligent platform. Happl is backed by leading investors such as YCombinator, 6Degrees Capital, and more, known for backing leading companies such as Deel, Rippling, Airbnb, Coinbase, Dropbox, and most recently was awarded a place in the UK’s top 100 startups for 2026. About the role As a Senior Backend Engineer at Happl, your mission is to build the systems that power a global, AI-first benefits platform. You’ll design, build, and scale backend services that are reliable, secure, and performant, enabling our product teams to move fast while supporting complex real-world use cases across payroll, finance, and employee benefits. This role is for someone who enjoys ownership, thrives in fast-moving environments, and wants to build foundational systems that directly impact how companies support their people. What you’ll be doing This role sits within our Engineering team and works closely with Product, Frontend, Data, and Customer teams across the full development lifecycle. You’ll help shape how we build and scale our backend by focusing on: - Designing and scaling the backend architecture powering a global, AI-first platform - Building and owning core services across benefits, allowances, payments, and reporting - Developing scalable data models and ensure integrity across systems - Improving platform reliability, performance, security, and observability - Automating workflows and Go Rules to streamline complex operations - Collaborating closely with product and frontend teams to ship end-to-end features - Writing clean, well-tested, production-ready code - Using AI tools to accelerate development and iteration - Contribute to architecture, technical decisions, and engineering standards You’ll play a key role in ensuring Happl’s backend scales as our customer base, features, and global footprint grow. What we’re looking for - 4+ years experience as a Backend or Software Engineer - Strong experience with modern backend languages and frameworks (e.g. Typescript, Golang) - Experience designing and consuming APIs (REST, event-driven systems) - Solid understanding of databases (SQL / PostgreSQL) and data modelling - Experience building and scaling production systems - Familiarity with cloud infrastructure and CI/CD workflows - Comfortable working with integrations and third-party services - Experience using AI tools (e.g. ChatGPT, Claude) as part of your workflow - Clear communicator who works well with both technical and non-technical stakeholders - Proactive, detail-oriented, and comfortable taking ownership If you don’t meet every requirement but feel this role fits your trajectory, we’d still love to hear from you. Why join Happl - Help shape the future of employee benefits - Competitive base salary and commission - Meaningful equity in an early stage growing business - Flexible hybrid working from day one - Access to your own Happl benefits platform - Optional enrolment in Private Health Insurance - Optional enrolment in Dental insurance, including family cover - A flexible Wellbeing budget to spend on whatever wellbeing means to you - Learning & Development (L&D) allowance - Pension scheme from day one - Rapid career progression in a scaling commercial team About the Interview - Call 1: 20-min Intro call with Ben (COO & CoS) - Call 2: 30-min deep dive with Lee (Head of Engineering) - Short Task - Call 3: 30-min deep dive with Ben T (CEO & Founder) Additional Details Location: London, Waterloo Team: Engineering Working arrangement: Hybrid (3+ Days in Office) #BS-L1