Full Stack Engineer

9fin; Greater London; Hybrid; GBP 70,000 - 90,000; Full time

Job summary

A leading AI platform for debt markets is seeking a Backend Engineer to develop systems and functionality for their platform using Python. The role involves collaborating with cross-functional teams to design and implement software that delivers value to clients. Ideal candidates will have experience in API development and a strong focus on code quality. Competitive salary and benefits are provided, along with opportunities for personal growth and flexibility in the workplace.

Benefits

Competitive salary

Equity options

Private Medical Insurance

Pension contributions

25 holiday days per year

Qualifications

• Experience working as a Full-Stack or Backend-leaning Engineer.
• Hands-on experience with Python and web frameworks.
• Knowledge of SQL for querying relational data.

Responsibilities

• Contribute to projects by helping design systems and deliver new functionality.
• Development primarily on backend services within the 9fin platform.
• Collaborate closely with Product and Clients on projects.

Skills

Python

API development

Collaborative communication

Code quality

Tools

Flask

FastAPI

PostgreSQL

Docker

Job description

About 9fin

9fin is the AI platform powering global debt markets — the world’s largest asset class at over $145 trillion.

Debt markets are vast, global, and mission-critical, yet still run on fragmented data, PDFs, and manual workflows. 9fin replaces this broken infrastructure with a single platform that centralises proprietary credit data, deep analysis, and high-value workflows across global markets.

Today, 9fin powers teams at 300+ blue-chip institutions worldwide, including global banks, asset managers, private equity firms, law firms, and advisors. The business is scaling at exceptional speed, with rapid expansion in the US and best-in-class retention driven by deep workflow adoption.

We’re at a defining inflection point. With proven product-market fit and strong, global market pull, 9fin is accelerating toward becoming the category-defining platform for debt markets worldwide.

What you’ll work on

• As part of a cross-functional team, contribute to projects by helping design systems, building proof of concepts, and delivering new service functionality — including APIs, data processing, and automation — while collaborating closely with Product and Clients.

• Development and engineering primarily on backend services and web-application–hosted tools and systems within the 9fin platform.

• Play an impactful role within project teams as an individual contributor, participating in code reviews, collaborating with peers, and contributing ideas during research and experimentation with new technologies.

• Continually improve the 9fin codebase by taking opportunities to automate, refactor, and document where it’s most valuable.

• Work across a diverse set of web platforms, including financial data modelling, access-control business logic, environmental and emissions data capture, integration with ML/AI prediction services, data visualisation, and automation systems.

• Collaboration and teamwork: All projects are delivered by cross-functional teams that include domain expertise from 9fin’s financial, legal, and editorial colleagues. You’ll work closely with non-technical stakeholders and help explain technical concepts in a clear, accessible way to support effective team progress.

• Developer experience: You’ll work within a strong developer experience setup, including automated preview environments, feature flags, and well-maintained non-production environments, enabling rapid iteration and feedback.

Our Backend Stack

• Python is the dominant backend language used

• Flask & FastAPI

• Typing is used within our Python stack to power automated documentation and API definitions

• Relational Databases (PostgreSQL) at the heart of majority of services

• We have our own internal developer platform with standardised paved road approaches to infrastructure to bring your code into production as quickly as possible.

• We’re AWS for Cloud hosted services

• Heavy use of AWS lambda Serverless

• Docker (AWS ECS) for uniform development/deployment from dev to prod

Requirements

This role will be a great fit if you:

• Have experience working as a Full-Stack or Backend-leaning Engineer within a product team, contributing to system design discussions and delivering production software.

• Can plan and reason about software effectively, clearly communicating how your work fits into larger systems and delivers value to clients.

• Have hands-on experience designing and implementing data flow through software, from persistent storage to API endpoints, applying industry best practices for validation and reliability.

• Have experience with Python and web frameworks (we currently use FastAPI with strong typing and Pydantic).

• Have experience building and consuming APIs, ideally within a service-oriented architecture.

• Have a working knowledge of SQL for querying and working with relational data.

• Are a collaborative and proactive communicator, comfortable working with engineers and non-engineers across the business.

• Care about code quality, writing testable and maintainable code, and actively participating in code reviews — both receiving feedback and reviewing others’ work.

Benefits

We’re a scaling start up and we enjoy sharing our success, when the company succeeds, we always reinvest that in our people. We also offer huge amounts of responsibility, an abundance of opportunity for growth and a platform to truly excel.

Financial & Insurance

• Competitive Salary (our salary bands are benchmarked at the top end of the market)

• Equity options

• Pension (your minimum contributions are 4% with 9fin matching up to 7%)

• Private Medical Insurance

• Paid sick leave with Income Protection for long periods of illness

• Group Life Assurance

• Season Ticket Loan & Cycle to Work schemes

Time off

• 25 holiday days per year

• Local public holidays (with the ability to exchange them for alternative days)

• Hybrid working model, to allow you the flexibility to decide how, where and when you do your best work

• Work abroad for up to 3 months a year

• 1 month paid sabbatical after 5 years of service

• Enhanced parental leave & flexible working arrangements available

Training & Culture

• Professional learning and development budget

• Quarterly team socials

• Summer and Winter company social events

9fin is an equal opportunities employer

At 9fin we are dedicated to building and promoting a fair and inclusive workplace where everyone can reach their full potential and truly belong. We recognize that building diverse teams enables a more creative and productive environment. If you’re excited about this role but your experience doesn’t perfectly align with the job description, we encourage you to apply anyway. You might just be who we’re looking for — either for this role, or perhaps another.