Senior AI Product Engineer

Plain

Plain is redefining customer support for the next generation of B2B companies. We’re building the fastest, most powerful platform to help companies move beyond reactive support and build true customer relationships. Some of the world’s most forward-thinking companies - like Cursor, Raycast, and Granola - trust Plain to unify all customer interactions, enable faster team collaboration, and supercharge their workflows with AI. B2B customer support is undergoing a seismic shift. AI is transforming the way companies engage with customers, shifting support from a siloed function to a company-wide effort across Slack, Discord, and any other channel you talk to customers in. The old way - slow, manual, and disconnected - no longer works. This role is hybrid with 3 days a week in our London office. WHAT YOU’LL DO We’re in a rare spot. Plain is already powering support for high-growth companies with a lightning-fast, deeply scalable platform. AI has been part of our DNA from the start. Now we’re doubling down to define how it shapes every layer of modern customer support. This is where you come in. We're looking for a customer obsessed Senior Product Engineer to help take our AI ambitions to the next level. You’ll build the Infrastructure that helps us build AI features quickly, safely and with confidence. You’ll own problems end to end, and play a key role in building a category-defining product. In this role, you will: * Own and ship AI features such as our agents, assistants, insights and more - from concept to production. * Design and implement backend services for AI integrations and data pipeline. * Build robust APIs and abstractions for internal AI usage * Drive system scalability: caching, optimization, processing patterns, etc * Contribute and drive the evolution of the infrastructure for AI including architecture, evaluation and iteration pipelines. * Solve complex AI challenges around AI accuracy, reliability, and quality – using rigorous quantitive approaches. * Advocate for our work externally – writing, speaking, and engaging with the broader AI community. THIS IS A GREAT FIT IF YOU… * Are an experienced backend engineer who’s shipped AI products in the OpenAI & Anthropic era – especially text and data-heavy AI applications. * Have hands-on experience with LLM orchestration and LLM API optimization (costs, latency, etc) * Are familiar with RAG architectures and technologies * Have AI observability experience. AI isn’t just about shipping features that sound great – it’s about knowing, conclusively, if they’re making things better. * Have a clear perspective on what makes a great AI product. We want to apply AI with precision, nuance, and real impact – not as a gimmick. * Are product minded and customer focused in how you build software. * Measure your success by user impact, not just technical elegance. * Are self-driven, impact-focused, and thrive in a fast-moving, high-ownership environment. * Bonus: you have experience with agent frameworks and design. THIS WON’T BE THE RIGHT ROLE IF YOU… * Have primarily academic or research ML/AI experience. This role’s looking for someone with Applied AI experience. * Think AI for support is just chatbots and deflection. B2B support is complex – we want AI through the platform, not just automating conversations. * Struggle with ambiguity. We’re an early-stage startup. Things change quickly, and often, knowing what to work on is as important as the work itself. * Prioritize working with the latest tech for its own sake. We choose tools that make us productive – not what’s trendy. (Postgres is great.) * Are looking for a management role. This is a hands-on individual contributor position. * Want the perks of a big company. We offer competitive compensation for our stage, but we’re a startup – this is a different kind of opportunity.

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.

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 Our AI product area is growing. We already have two Product Managers working across conversational AI, agentic workflows, and domain-specific automation, and we need a third to expand our capacity as the scope of AI at 9fin accelerates. Backed by over $170M in funding (Series C), we are scaling rapidly across product, engineering, and go-to-market. AI is not a bolt-on feature at 9fin; it is the core differentiator for the next phase of the company. You will join an established AI PM team and take ownership of a product area within our AI surface. This could span new AI-powered features for credit analysts, workflow automation for legal and financial analysis, or expanding our conversational AI into new domains. The team has already built evaluation infrastructure and quality frameworks; you will use and contribute to these rather than build them from scratch. You will work within our product organization (eight squads across AI, data, and domain verticals) and partner closely with ML engineers, data scientists, domain experts, and designers. This is a high-autonomy role with real scope to shape what 9fin's AI products can do for our clients. WHAT YOU'LL DO PRODUCT STRATEGY & EXECUTION * Collaboratively create and champion a clear product vision and strategy for your area, with a focus on building and evolving our AI products * Synthesize qualitative and quantitative insights into problem statements that identify root causes, not just symptoms * Shape the next generation of agentic AI products: multi-step reasoning workflows, tool orchestration, and autonomous task completion for financial professionals * Demonstrate a working understanding of the challenges specific to building with LLMs, including managing hallucinations, evaluating output quality, and designing for non-deterministic systems * Use confidence-building methods (prototypes, user research, data analysis) to understand how users will interact with AI-powered products before committing to full builds AI QUALITY & DATA * Use the team's AI evaluation framework (LLM-as-judge protocols, quality thresholds, SME eval cycles) to validate and improve the products you ship * Contribute to the data strategy for your product area: annotation quality, ground truth curation, and feedback loops that improve model performance over time * Proactively identify and track metrics that measure client and business benefit, working with the team on continuous model evaluation and improvement TEAM LEADERSHIP & COMMUNICATION * Create a collaborative environment for your squad, providing wider context and clear goals so everyone can do their best work * Work with data scientists and ML engineers to bridge the gap between business needs and the technical capabilities of AI models * Communicate strategy, initiatives, and progress transparently across the organisation * Translate complex AI concepts, capabilities, and limitations into language that non-technical stakeholders can act on * Champion responsible AI practices: transparency in model outputs, bias monitoring, and compliance with client expectations around AI-generated content WHAT WE'RE LOOKING FOR * 5+ years of product management experience, preferably in FinTech or B2B SaaS, with at least 2 years focused on ML or GenAI products * Working knowledge of RAG architectures, embeddings, prompt engineering, and LLM evaluation methods (not just "AI concepts" at a high level) * Experience shipping AI products where output quality is probabilistic: you know how to define "good enough" and iterate from there * Comfortable reading Python notebooks and SQL to interrogate model outputs and usage data * Track record of shipping AI products where you managed the tension between ML research/exploration and production delivery constraints * Collaborative leadership style with strong stakeholder management; you build relationships that empower your team to achieve outcomes * User-centric communication skills: you can explain AI capabilities and limitations to clients and internal stakeholders without overselling or underselling * You thrive in fast-paced, ambiguous environments and are energised by the challenge of building something new NICE TO HAVE * Experience in financial services, legal tech, or data/analytics platforms * Familiarity with credit markets, debt instruments, or regulatory/compliance workflows * Experience with NLP applied to document analysis (contracts, legal filings, financial reports) * Experience with agent orchestration frameworks, tool use patterns, or multi-step AI workflows BENEFITS * Competitive, market-benchmarked salary * Pension with 7% company matching * Private medical insurance, paid sick leave, income protection, group life assurance * Season ticket and cycle-to-work schemes * Hybrid flexibility with up to 3 months annual work abroad * 25 holiday days plus local public holidays (exchangeable) * One-month paid sabbatical after 5 years; enhanced parental leave * Professional development budget and regular social events We will be reviewing all CVs the w/c 13th July, and will follow up then 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.