Staff Engineer (GenAI Core) in London

About Pleo. Messy spend management is tricky business. And tedious processes are a lose-lose situation for all involved, not just finance. At Pleo, we're changing that. We build spend solutions that make managing money seamless, empowering, and surprisingly effective for finance teams and employees alike - with a vision to help all businesses ‘go beyond’. The word ‘Pleo’ actually means ‘more than you’d expect’, and living by that mantra has been the secret to our success over the last 10 years. Now, we’re at a pivotal moment in our journey; every move we make has a direct impact on our 40,000+ customers, our business, and our collective success. We need people who take pride in uncovering customer needs, who turn complex problems into simple solutions, challenge the way things are done (respectfully), and always aim high. With great ambitions driving us forward, we can’t say we’ve got this whole thing figured out. And frankly, that’s half the fun! What we can say is that we’re a driven, progressive, and, importantly, a kind bunch of 850+ people from over 100 nationalities, all committed to delivering the future of business spending, together.

At Pleo, we're on a mission to make spend management surprisingly effective and empowering. We're hiring a Staff Engineer to join the GenAI Core team. You will help set technical direction for Pleo's AI platform, the shared infrastructure that enables product teams across the company to build AI-powered features reliably and at scale.

What GenAI Core Does

GenAI Core owns and operates Pleo's AI platform infrastructure. We are the team that makes it possible for every other product team at Pleo to build AI-powered features, reliably, observably, and without reinventing the wheel. That means:

• LLM routing and access: a centralised LLM proxy layer (LiteLLM) that routes requests to different model providers (Azure OpenAI, AWS Bedrock, Google Gemini), with budget enforcement and rate limiting
• Observability and evaluation: integrations and tooling (BrainTrust) to monitor, log, and evaluate LLM calls in production, supporting both automated evaluation and human review
• Platform standards and guidance: we define how AI is done at Pleo, providing patterns, contracts, and shared components that product teams build on
• Internal consulting: as product teams across Pleo adopt AI capabilities, GenAI Core will increasingly act as a technical partner, helping teams design and implement AI features correctly on top of the platform

This is software engineering work. While the domain revolves around AI infrastructure, you will spend most of your time building reliable, scalable backend systems.

What You’ll Be Doing

In this role, you will be a force multiplier for platform quality and technical direction.

• Drive the design, delivery, and evolution of the GenAI Core platform, the shared AI infrastructure used by all product teams at Pleo
• Own and evolve service architecture, APIs, and integration contracts, with a high bar for reliability and observability
• Set technical direction for key parts of the platform, including LLM routing, budget enforcement, observability pipelines, and evaluation infrastructure
• Lead cross-team technical initiatives and act as a trusted technical partner when product teams need to build AI-powered features on top of the platform
• Raise the engineering bar through strong practices: code reviews, incident follow-ups, safe change management, and resilient system design
• Proactively identify and address technical debt, and guide the team through architectural decisions and migrations
• Support other engineers through pairing, reviews, and technical guidance
• Contribute hands-on in code. You should expect to be coding a meaningful part of the time.

You’ll Bring Solid Experience With

• Designing and maintaining backend systems with strong requirements for reliability and observability
• Building and operating a shared platform or infrastructure components used by multiple teams
• Distributed systems fundamentals, including async workflows, idempotency, consistency, and designing for failure
• API design, clear service boundaries, and integrating with external systems in a maintainable way
• Observability and owning systems in production, including monitoring, alerting, incident response, and post-mortems
• Strong testing practices and a high quality mindset
• Clear communication and pragmatic decision-making across teams and stakeholders

Nice to have

• Hands-on experience working with LLM APIs (OpenAI, Anthropic, AWS Bedrock, or similar) in a production system
• Familiarity with LLM evaluation patterns such as LLM-as-judge, vector similarity, and sampling strategies
• Experience building or operating proxy or routing layers for AI workloads

Your colleagues would say you

• Lead by example and raise the bar with pragmatism and care
• Communicate clearly, listen well, and bring people along in decisions
• Enjoy breaking down complex problems, gathering input, and driving to a solution
• Coach and mentor others and create space for people to grow
• Prefer progress over perfection, while still caring deeply about quality

Show me the benefits!

• Your own Pleo card (no more out-of-pocket spending!)
• Lunch is on us for your work days - enjoy catered meals or receive a lunch allowance based on your local office
• Comprehensive private healthcare - depending on your location, coverage options include Vitality, Alan or Médis
• We offer 25 days of holiday + your public holidays
• For our Team, we offer both hybrid and fully remote working options
• We use MyndUp to give our employees access to free mental health and well-being support with great success so far
• Paid parental leave - we want to make sure that we're supportive of families and help you feel that you don't have to compromise your family due to work

About Your Application

• English first. Since it's our company language, please submit your application in English. You’ll be using it a lot if you join us.
• A fair look for everyone. Our talent team reads every single application to ensure the process is fair. To keep things running smoothly, we only accept applications through our system—our support team can’t pass on calls or emails.
• Diversity drives us. We can only reach our goals if our team reflects the world around us. That starts with you hitting apply, even if you don't tick every single box. We encourage people from all backgrounds and experiences to join us.
• Interview at your best. We want you to feel comfortable throughout the process. If you have any accessibility requirements or need a specific format, email. We’ll design a process that works for you.
• Your data is safe. When you apply, we process your personal data as a data processor. For more information on how Pleo processes personal data, read our Privacy Policy here.
• Applying for multiple roles? Nothing is stopping you, and we assess every role independently. However, we do look for alignment, so make sure you can explain why your interest and experience are right for each specific role.
• Reapplying. If you’re applying for the same role again, please wait six months from your last decision before hitting submit.