Senior Software Engineer AI in London

Build the backend foundations for Spendesk’s AI-native experiences. Spendesk is looking for a Senior Backend Software Engineer (IC4) to join our PDE (Product, Design & Engineering) organization and help shape the technical foundations of our next generation of AI-powered product experiences. This is a senior, hands-on role for an engineer who combines strong backend fundamentals with solid fluency in LLM-enabled systems. You will work on the technical foundations behind conversational and agentic experiences: backend services for context handling, orchestration, tool calling, and reliable interactions with LLMs and applicative systems.

You will partner closely with a Staff Engineer (IC5) on the same scope. Together, you will shape and implement the architecture that enables AI systems to interact safely and efficiently with Spendesk’s product ecosystem. While the IC5 is expected to drive more transversal and system-wide architecture topics, you will be a key senior builder on these foundations, owning complex services end-to-end and helping turn architectural direction into production reality.

About The Role

As a Senior Backend Software Engineer (IC4), you will help create the backend layer that supports agentic and conversational experiences for Spendesk end users.

Your Scope Will Include Services That:

• manage conversations and contextual state,
• support ingestion and retrieval of rich content such as PDFs and images,
• integrate LLMs through AWS Bedrock with robust operational patterns,
• connect to MCP-compatible services and tools exposed by other squads,
• orchestrate multi-step workflows combining reasoning, tool usage, and product actions.

This is not just about integrating services’ features to an LLM. You will build production-grade services that need to be reliable, observable, secure, and designed for long-term extensibility. You will contribute to reusable patterns and collaborate with ML Engineers, Product Managers, Designers, and applicative squads to make these foundations useful across multiple AI use cases.

Our tech environment

You’ll operate in a modern engineering environment designed for both product delivery and AI integration:

• TypeScript
• Node.js for backend and banking applications
• React on the frontend
• PostgreSQL for data storage; Redis, SQS, and Kafka for jobs, queues, and event streaming
• Terraform to define infrastructure as code
• Kubernetes, Lambdas, and Step Functions to run our applications
• AWS as our cloud provider, including AWS Bedrock for LLM access
• GitHub Actions for CI

Key responsibilities

Backend services for AI-native experiences

You Will:

• Design, build, and operate backend services and APIs that power conversational and agentic AI features.
• Implement the services needed for context management, tool invocation, rich content access, and multi-step orchestration.
• Build robust patterns for integrating LLMs through AWS Bedrock, including retries, fallback, tracing, and cost-aware usage.
• Ensure these services are designed for production from day one, with strong standards on reliability, maintainability, and security.

Architecture & transversal system design

You Will:

• Partner with the IC5 Staff Engineer to implement the architecture supporting AI-native product experiences.
• Contribute to reusable service boundaries, contracts, and interfaces that can be adopted across squads.
• Help define how applicative squads can expose MCP-compatible tools and capabilities to central AI services.
• Translate high-level architectural direction into concrete technical implementations and scalable engineering patterns.

Hands-on delivery of complex systems

You Will:

• Own complex backend components end-to-end, from design and implementation to deployment and maintenance.
• Contribute directly to proof-of-concepts and experiments, then harden the successful ones into reliable production services.
• Review code, challenge design decisions, and raise the quality bar on backend engineering within the squad.
• Bring pragmatism to delivery, balancing speed of experimentation with long-term platform quality.

Observability, performance & operational excellence

You Will:

• Instrument services with logs, tracing, and metrics to ensure strong production visibility and fast iteration.
• Help define and uphold quality standards around latency, failure handling, cost efficiency, and resilience.
• Contribute to a “you build it, you run it” culture, where backend engineers own what they ship in production.
• Ensure AI-related services are built with secure coding and responsible data handling practices.

Cross-functional collaboration

You Will:

• Collaborate with Product Managers and Designers to turn AI product concepts into concrete backend capabilities.
• Partner with applicative squads to connect backend services with the tools, context, and business actions needed by AI systems.
• Help create shared engineering knowledge around LLM integration, async workflows, and reliable AI feature delivery.

What we’re looking for

Experience & background

You Have:

• Significant experience on backend software engineering experience in production environments.
• A strong track record of designing and shipping scalable backend services with clear ownership of reliability and maintainability.
• Experience contributing to complex technical projects in fast-paced product organizations.
• Ideally, hands-on exposure to AI-enabled or LLM-backed product features in production.

Technical & data skills

You Have:

• Strong backend engineering skills with TypeScript / Node.js or adjacent technologies.
• Good fluency in service design, asynchronous architectures, and resilient distributed systems.
• Experience integrating APIs and external services into robust product backends.
• Practical experience, or strong interest, in integrating LLMs into production systems, ideally using platforms such as AWS Bedrock, OpenAI, or Anthropic.
• Familiarity with technologies such as Kafka, SQS, Step Functions, PostgreSQL, and modern observability practices.

Leadership & collaboration

You Are:

• Highly autonomous and comfortable owning ambiguous technical problems from framing to delivery.
• Able to work effectively in partnership with a Staff Engineer while independently delivering complex components.
• Product-minded, customer-focused, and capable of translating business needs into backend systems.
• Curious about AI-native product design and motivated by building durable foundations, not just short-term demos.
• Fluent in written and spoken English, our business language.

Nice To Have

• Experience with conversational or agentic systems
• Experience integrating LLMs with tool-calling, guardrails, and evaluation loops
• Experience with rich content processing, document workflows, or multimodal service design
• Experience in SaaS, fintech, or regulated environments

Not ticking every box? We’d still love to hear from you. At Spendesk, we value skills, potential and diverse experiences. If this role excites you and you believe you could contribute, we encourage you to apply.

How we work

• AI-first, product-led: prototype fast, dogfooding, iterate based on data
• You build it, you run it: owning deployment, monitoring, and continuous improvements
• Collaboration by default: PM, Design, ML Engineering, and Backend Engineering work together toward outcomes
• Pragmatic engineering: we optimize for impact, not theoretical perfection

What success looks like in your first 90 days

• You’ve shipped or materially advanced a production-grade backend component that supports conversational or agentic AI experiences at Spendesk.
• You’ve partnered effectively with the IC5 Staff Engineer to turn architectural direction into reliable, reusable backend services.
• You’ve integrated at least one LLM-backed capability through AWS Bedrock with appropriate observability, retries, and operational safeguards in place.
• You’ve improved one shared engineering capability, for example orchestration patterns, service contracts, or cost/reliability monitoring, that can be reused by future AI features.

Location and ways of working

We value regular in-person collaboration. We’re primarily hiring in Paris, London or Barcelona with a flexible hybrid setup. Outstanding remote candidates may be considered, but this is not a remote-first role.

Hiring Process

• HR screening call
• Discussion with the Hiring Manager
• Technical interview, live coding and/or system design depending on profile
• Final interview with leadership

As we are an international team, please submit your application and CV in English.

About Spendesk

Spendesk is the AI-powered spend management and procurement platform that transforms company spending. By simplifying procurement, payment cards, expense management, invoice processing, and accounting automation, Spendesk sets the new standard for spending at work. Its single, intelligent solution makes efficient spending easy for employees and gives finance leaders the full visibility and control they need across all company spend, even in multi-entity structures. Trusted by thousands of companies, Spendesk supports over 200,000 users across brands such as SoundCloud, Gousto, SumUp, and Bloom & Wild. With offices in the United Kingdom, France, Spain and Germany, Spendesk also puts community at the heart of its mission.

For more information:

• Flexible on-site and remote policy
• Latest Apple equipment — the tools you need to excel
• Access to Moka.care — for emotional and mental health wellbeing
• Great office snacks — to fuel your day
• A positive team to work with daily!

We also offer location-specific benefits tailored to each market, including health insurance, wellness allowances, commuter support, meal vouchers, and gym memberships — ensuring you're well supported wherever you're based.

Diversity & Inclusion

At Spendesk, we're committed to fostering an environment where all differences are encouraged, supported and celebrated. We're building our culture for everyone, with everyone. Our goal is to attract and build a diverse, equal and inclusive team, where everyone feels welcome and we truly embrace and encourage people from all backgrounds to apply.