Senior Backend Engineer - Developer Experience

9fin

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 The team maintains a strong focus on impact, using technology to deliver value for the business. While we have a high-level vision from the business, we have autonomy to set our team goals and define our own success. We take responsibility for our outcomes and emphasize proactive behaviours like ownership and accountability. * As part of a cross functional team, lead projects by defining and designing systems, building proof of concepts, and delivering new service functionality - including APIs, data processing and automation - while collaborating with Product and Clients * Development and engineering primarily on the backend services and web application hosted tools and systems of the 9fin platform. * Play an impactful role within project teams as a senior IC, running code reviews, mentoring other developers, leadership & involvement in early research and experimentation with new technologies providing input for new features and products. * Continually improve the 9fin codebase taking the chance to automate, refactor and document when it’s most impactful.. * Very diverse web platforms, from complex financial data modelling, complex access control business logic, capturing environmental, emission, energy data, incorporation of ML/AI prediction services, data visualisation serving and automation systems. * Collaboration and teamwork: Cross functional teams are formed for all projects including the appropriate domain expertise from 9fin financial, legal and editorial colleagues. This allows the best quality information and feedback to go directly to engineering project teams. Your ability to explain and break down complex projects to non technical audiences will enable productive and efficient team progress. * Developer Experience: Through managed automated preview environments, feature flags and well maintained non production environments. You will be able to move with velocity and get feedback and iterate quickly. 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 operating as a Senior IC Engineer, leading systems design and infrastructure discussions, mentoring more junior team members, and scoping work within cross-functional product teams. * Plan and reason about software effectively, clearly and compellingly communicating its purpose within systems and its business impact on clients * Have hands-on experience designing data flow through software, from persistent storage to API endpoints, while applying industry best practices for validation * Experience with Python and its web frameworks (we currently use FastAPI with strong typing & Pydantic) * Strong experience delivering APIs, Service Oriented Architecture * Strong working knowledge of SQL statements for retrieving data * A good collaborator and communicator with cross functional engineering teammates and others within 9fin * Code Quality: Through writing testable, maintainable code, and by engaging in code review for your own work and for reviewing others Nice-to-have: * Experience in data modelling and with a pipeline orchestrator 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.

9fin

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. We're looking for a Senior Engineer II to take broad technical ownership of the backend systems powering 9fin's platform. You will sit between our Senior and Staff engineering tracks. You will own meaningful systems end to end, lead multi sprint initiatives across a product domain, and shape how we build for scale. You will operate as a strong senior IC, leading design, raising the engineering bar through review and mentorship, and partnering closely with Product, Data, and our financial and legal domain experts. This role suits someone who has already grown beyond a typical senior remit. You enjoy diving into distributed systems problems, and you have firsthand experience scaling services under real production load. WHAT YOU'LL DO * Own the design and delivery of significant backend systems and services across a product domain, from data modelling through API surface to operational concerns. * Lead complex, multi sprint engineering initiatives that span several engineers and stakeholders. * Drive scaling work: identify bottlenecks, propose architectural changes, and execute migrations safely in production. * Make pragmatic decisions about distributed systems concerns including consistency, idempotency, partitioning, retries, and observability. * Contribute to platform level discussions on service boundaries, data ownership, and how systems evolve as we enter new markets. * Run thorough code reviews, mentor senior and mid level engineers, and help define what good looks like in the codebase. * Partner with cross functional teammates from Product, Data Engineering, and our editorial and legal domain experts to scope work and ship the right thing. * Improve developer experience by investing in tooling, testing, observability, and the paved road so the whole team moves faster. * Ramp on legacy areas of the system, find the highest leverage cleanup, and execute it without stalling delivery. * Use AI assisted engineering to move faster on understanding, prototyping, and shipping code. OUR BACKEND STACK * Python is the dominant backend language. * Flask and FastAPI, with strong typing and Pydantic powering automated documentation and API definitions. * PostgreSQL at the heart of most services. * AWS for cloud hosted services, with heavy use of AWS Lambda serverless. * Docker on AWS ECS for uniform development and deployment. * Internal developer platform with a standardised paved road from code to production, plus managed preview environments and feature flags. WHAT WE'RE LOOKING FOR You will be a great fit if you have: * Several years operating as a senior backend engineer, with a clear track record of leading technical initiatives end to end across a product domain. * Experience contributing to the design of distributed systems in production, including the operational realities such as failure modes, observability, data consistency, and graceful degradation. * A track record of solving scaling problems, whether database scaling, throughput, latency, or cost. You can talk through a real example end to end: how you measured the problem, what you changed, and what the outcome was. * Experience designing and operating event driven architectures in production, including message queues or streaming systems, with a clear understanding of delivery guarantees, idempotency, and failure handling. * Strong design skills around APIs, service boundaries, and the flow of data from persistent storage through to clients. * Strong Python experience, including modern web frameworks (we use FastAPI with Pydantic and strong typing). * Deep working knowledge of SQL and relational data modelling. * Excellent collaboration and communication, including the ability to explain complex systems and tradeoffs to non technical stakeholders. * A strong product and customer mindset, with the judgement to balance shipping value against long term system health. * A high bar for code quality, testability, and operational maturity, and the habit of raising that bar through review and mentorship. Nice to have: * Experience working on complex permissioning or access control systems (multi tenant, role or attribute based, fine grained, audit driven, or similar). * Experience with end to end document management systems, especially solving problems of scale and applying strong security practices such as encryption, access control, data lineage, and retention. * Experience modernising legacy systems and migrating workloads with minimal downtime. * Experience with a data pipeline orchestrator. * Experience working at AI startups, including integrating with and building on top of AI and LLM based solutions. COMPANY 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) * 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.

9fin

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. THE OPPORTUNITY The AI Engineering team at 9fin is building the next generation of AI capabilities that will power our products for years to come. We're looking for a Senior AI Platform Engineer to help design, build, and evolve the core AI platform that enables Generative AI, Agentic AI, and machine learning applications across the business. This is an opportunity to join at the beginning of the platform's journey. Rather than inheriting a mature internal platform, you'll help shape its architecture, define engineering standards, and build reusable infrastructure that allows AI teams to move quickly, safely, and at scale. Working alongside backend engineers and AI engineers, you'll create the shared platform services that power everything from intelligent document understanding to autonomous AI agents capable of running scheduled workflows, generating morning briefings, identifying distressed companies, and supporting future AI-powered product experiences. Every day is different, but here's an example of the kind of things you'll work on: * Design, build and continuously evolve the enterprise AI platform that powers AI products across 9fin. * Develop scalable AI services supporting Agentic AI, Retrieval-Augmented Generation (RAG), embeddings, vector search, model serving, and intelligent automation. * Build orchestration layers that transform structured and unstructured enterprise data into reusable AI capabilities. * Develop production-ready AI applications using modern LLM frameworks and orchestration tools. * Design reusable platform components for prompt management, model serving, vector search, embeddings, AI gateways, and evaluation services. * Build APIs, SDKs, and developer tooling that enable self-service AI development across engineering teams. * Design secure, scalable deployment pipelines for AI models and applications. * Build AI observability capabilities including monitoring, tracing, evaluation, cost optimisation, and production quality measurement. * Collaborate closely with AI Engineers, Backend Engineers and Engineering Leadership to define platform architecture and engineering standards. * Establish engineering best practices around testing, governance, Responsible AI, deployment, and operational excellence. * Continuously evaluate emerging AI technologies and evolve the platform as the ecosystem rapidly advances. WHAT MAKES THIS ROLE DIFFERENT Unlike many AI Platform roles that focus on maintaining existing infrastructure, this role is centred around building the platform from the ground up. You'll join at an early stage where many architectural decisions have yet to be made, giving you genuine influence over how AI is built, deployed, and operated across 9fin. Within your first six months, you'll help build the platform that powers production AI agents capable of running autonomously in the background—supporting workflows such as scheduled market briefings, distressed company discovery, and future intelligent financial research products. Rather than owning a single AI product, you'll build the shared capabilities that enable multiple engineering teams to rapidly develop, deploy, and operate AI solutions at scale. You'll be one of a small number of senior engineers helping shape the technical direction of the platform alongside the Engineering Lead and fellow senior engineers. ABOUT YOU This role will be a great fit if you: AI PLATFORM ENGINEERING * Have 5+ years of software engineering experience, including 2+ years building AI/ML platforms, Generative AI applications, or production machine learning systems. * Have experience designing and deploying enterprise AI applications into production with a strong focus on scalability, reliability, and developer experience. LLMS & AGENTIC AI * Have hands-on experience building applications powered by Large Language Models (LLMs). * Have experience building Model Context Protocol (MCP) and Retrieval-Augmented Generation (RAG) solutions, making use of embeddings, vector databases, and modern LLM orchestration frameworks. * Have experience building or contributing to agentic AI systems, intelligent workflows, or orchestration frameworks. BACKEND & PLATFORM ENGINEERING * Are a strong backend engineer with production experience using Python and/or TypeScript. * Have designed scalable backend services, REST APIs, and event-driven architectures. * Have experience building reusable platform capabilities, internal developer tooling, SDKs, or shared engineering services. CLOUD & INFRASTRUCTURE * Have strong experience building cloud-native applications. * Are comfortable working with Docker, Kubernetes, CI/CD pipelines, and containerised deployments. * Have experience with solutions such as AWS Bedrock and AgentCore * Understand how to deploy, monitor, and operate AI services in production. AI OPERATIONS & OBSERVABILITY * Have experience implementing monitoring, tracing, evaluation, and cost optimisation for AI systems. * Have experience with observability solutions such as Arize Phoenix, Langfuse, or Langsmith * Understand the operational challenges of deploying LLM-powered applications, including latency, reliability, hallucination monitoring, and model quality evaluation. COLLABORATION & TECHNICAL LEADERSHIP * Enjoy collaborating across multiple engineering disciplines to shape technical direction and establish engineering best practices. * Are comfortable operating as one of a small number of senior engineers, influencing architecture and platform direction without necessarily having formal management responsibilities. * Thrive in fast-moving environments where many platform capabilities are still being designed and built. BONUS POINTS Experience with any of the following would be highly advantageous: * AI gateways and model routing * Prompt management platforms * AI evaluation frameworks * LangGraph, LangChain, LlamaIndex, DSPy, CrewAI or similar orchestration frameworks * Vector databases and semantic retrieval * Knowledge graphs or document understanding systems * Building internal AI platforms used by multiple engineering teams 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 * 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 * AI experimentation budget of £800 (UK) per employee to trial AI tools * 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.