Senior Backend Engineer

About Junior

Junior is building the AI operating system for investment research. Our software helps private equity firms, consultants and financial institutions complete high-stakes research workflows dramatically faster - from diligence and memo writing to market mapping, research synthesis and strategic analysis.

We’re trusted by several of the world’s top private equity firms, Big Four consultancies and leading financial institutions.

• Bootstrapped and profitable
• ~£20M+ in revenue, after growing 10x last year
• 60+ people across the company
• 20-person engineering team, doubling to 40 this year
• Core stack: TypeScript, Next.js and PostgreSQL

You’d be joining early enough to shape the product, engineering culture and company, but with enough traction that everything you build lands immediately in front of demanding, paying customers.

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

Interview process

The process moves in days, not months:

1. Introductory call : background, motivation and mutual fit
2. Live technical screen (30-mins ): solving a Python problem live in an IDE with one of our engineers. We optimize for speed and completeness over polish, and the interview is completed without AI tools
3. On-site Interview : a full afternoon of coding, a system-design whiteboard and a product discussion with one of our PMs
4. Final Cultural Round : a final conversation about how you work, what motivates you and whether Junior is the right environment for you
5. Offer : decisions are made collectively and quickly

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, including:
• 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
• If you’re excited to drive innovation at Junior, we’d love to hear from you!

#J-18808-Ljbffr

Full job description from WhatJobs. Apply for this role →