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:

• Lunch + dinner provided in-office

• 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