Senior Backend Engineer - London

ABOUT JUNIOR We’re building cutting-edge LLM-powered workflow tools to supercharge investment research for private market investors. Our clients include most of the global top 10 private equity and consulting firms

• Junior already powers hundreds of billions of dollars invested annually. We’re a profitable, bootstrapped company with a growing team of 40+ based in London, NYC and Sydney. We 10x’d our revenue in 2025. You can read more about the company mission & values here https://myjunior.notion.site/join-junior-2026?source=copy_link. ROLE DESCRIPTION You’ll build and scale the systems that power our AI-driven research products and enable our operations / sales teams to deliver our product as efficiently as possible. This is a systems-level role - ideal for engineers who love thinking about data flows, orchestration, and performance across complex distributed systems. You’ll have the opportunity to:
• Ship quickly
• Architect and scale backend systems that support high-throughput LLM interactions, vector search, and multi-agent orchestration.
• Stitch together AI infrastructure across model providers, data stores, and internal APIs to create cohesive, performant systems.
• Prototype new backend capabilities (retrieval pipelines, caching layers, async task queues) that let us build faster and smarter
• Own the architecture of internal data systems and pipelines
• Build automation and integrations across product, CRM, and financial systems
• Help shape engineering culture and internal infrastructure decisions ABOUT YOU We’re looking for a Backend Engineer who enjoys building systems that make a company run better. You might be a good fit if you:
• Are based in London and excited to work from our Farringdon office (5 days/week)
• Have experience owning technical projects end-to-end, from architecture through production
• Are excited by the intersection of AI infrastructure, financial systems, and backend engineering
• Enjoy translating business problems into clean technical systems and automation
• Have worked with PostgreSQL and care about data modelling, reliability, and system design
• Write production code in Python, or TypeScript
• Are comfortable building APIs, internal tools, workflows, and infrastructure that support real customers
• Thrive in fast-moving startup environments and enjoy shipping quickly while maintaining strong engineering standards Bonus points for experience working on:
• Billing, payments, usage-based pricing, or financial workflows
• Internal infrastructure / dev tools at startups
• Data pipelines, workflow orchestration, or event-driven systems
• Retrieval, embeddings, or prompt orchestration Why Junior
• Top 1% traction: 0-20+ m rev in 3 years, fully bootstrapped / profitable, top-tier customers inc. some of MBB, Big 4, Top 5 PE mega-funds
• Flat org structure: lean startup environment – every engineer reports directly to the CTO / co-founder
• Competitive salary + equity and first-class benefits inc:
• Team lunch provided everyday at the London HQ!
• Third Space membership
• Private health insurance
• Multiple all-expense paid offsites per year (last 3 trips include Crete, Greece; Cancun, Mexico; Barcelona, Spain)
• Visa sponsorship available