Backend Engineer

About the role

In this role, you will own the design and delivery of critical backend services that form the core of the 9fin platform. You will be responsible for translating complex financial data requirements into robust, scalable software solutions that power global debt market workflows. You will lead the technical discovery for new features, creating proof of concepts that validate architectural approaches and drive product direction. You will work hand in hand with Product and Client teams to define system boundaries, ensuring the technical design aligns with strict market and compliance needs. A key part of your ownership will be mentoring junior developers, conducting code reviews, and elevating the overall engineering standard across the team. You will take end-to-end responsibility for service reliability, performance, and maintainability in production environments. This position requires you to balance rapid experimentation with the delivery of production-grade infrastructure that our institutional clients depend on. Your work will directly influence how 300+ blue-chip institutions manage billions of dollars worth of data and workflows.

Key facts

What you'll do

Architect and build backend services using Python, defining clear API contracts and data models for new 9fin features.

Lead the research and prototyping of new technologies, evaluating their fit for production use within the 9fin stack and debt market context.

Design and implement data routing and processing pipelines that handle complex financial information at scale and with high integrity.

Collaborate with domain experts to automate and streamline manual workflows, replacing error-prone processes with reliable software systems.

Write high-quality code and lead code reviews, ensuring best practices for maintainability, testing, and documentation are followed by the team.

Develop and maintain web application hosted tools that provide clients with deep insights into credit markets through intuitive interfaces.

Partner with cross-functional teams to translate business requirements into technical specifications that guide the implementation of new services.

Integrate machine learning and AI prediction services into existing financial data workflows, ensuring outputs are accurate and actionable.

Manage the full lifecycle of backend services on AWS, from initial deployment through to monitoring, scaling, and continuous improvement.

Champion developer experience by building and maintaining internal tools, automated preview environments, and feature flags that accelerate delivery.

Contribute to the strategic direction of the 9fin platform, identifying opportunities to refactor, automate, and document critical components.

Ensure data models and API designs account for how information flows from ingestion through persistent storage to real-time endpoint responses.

Take ownership of service reliability, debugging complex issues in distributed systems and resolving them with minimal disruption to clients.

Act as a technical leader within project teams, communicating progress and constraints to both technical and non-technical stakeholders.

Requirements

You must have experience planning and reasoning about software architecture, understanding how components fit into larger business systems.

You should be able to think critically about data flow, from persistent storage through to API endpoints, ensuring consistency and performance.

You must have strong experience with Python and its web frameworks, including Flask and FastAPI, and understand when to apply typing for API definitions.

You need a proven track record of delivering APIs and building services using Service Oriented Architecture in production environments.

You should possess good working knowledge of SQL for writing complex queries that retrieve and manipulate financial data.

You must be a strong collaborator and communicator, able to work effectively with cross-functional engineering teams and stakeholders.

You are expected to write testable, maintainable code and actively participate in code reviews to improve quality across the 9fin codebase.

You must be comfortable working within a fast-paced environment where requirements evolve and technical debt must be managed responsibly.

Nice to have

Experience working with AWS services such as Lambda, ECS, and other serverless or containerised platforms.

Familiarity with financial data models, particularly in the context of debt, credit, and ESG information.

Knowledge of modern data stack components, including data warehouses and orchestration tools.

Experience contributing to open source projects or publishing reusable libraries for Python services.

Practical notes

This is a full-time position based in London.

The role operates within a hybrid working model, allowing flexibility in how and where you work.

Candidates must be eligible to work in the United Kingdom without sponsorship.

Successful candidates will have the opportunity to work abroad for up to 3 months annually.

After 5 years of service, employees are eligible for a 1 month paid sabbatical.

Enhanced parental leave and flexible working arrangements are available to support an inclusive work environment.