Senior Software Engineer (London)

Core responsibilities include:

• Own revenue-critical event infrastructure. You'll work on systems that process customer usage data on which billing and invoicing depend. Design event streaming pipelines that handle high throughput with low latency. Build robust systems where data accuracy is non-negotiable and uptime is measured in nines.
• Design scalable data systems. You'll work with event streaming architectures, building sophisticated ingestion pipelines and query optimization strategies. Our event volumes grow with every new customer, so you'll architect systems that scale efficiently while keeping costs reasonable.
• Shape our backend architecture. You'll tackle our most complex technical challenges and set the standards for how we solve them. Our services run on Kotlin with Spring Boot, and you'll have significant influence over architectural patterns and how we approach infrastructure problems.
• Build for the next phase of growth. You'll design systems that work beautifully today and scale to 10x the load tomorrow. This means thinking about data storage strategies, horizontal scalability, and how your architectural decisions affect performance as volume increases.
• Drive impact on a small team. We've built an engineering culture around collaboration, learning, and shipping. You'll have significant influence on what we build, how we build it, and how we work together.

You should apply if

You're a builder who wants to solve problems end-to-end:

• You've shipped production backend systems and care about the difference between "it works" and "it's reliable"
• You care about customers - you want to understand why you're building something, not just what
• You’re comfortable with ambiguity. You thrive in early ideation stages, share work-in-progress to gather feedback, and adapt easily based on input
• You communicate clearly. Thoughtful communication is a superpower that sharpens how we collaborate and build
• You're interested in distributed systems and writing resilient software

Nice to have: Deep relational database expertise. We do a lot of complex queries and care about performance.

This might not be right if

We're a small team moving fast on hard problems. That might not be a fit if you:

• Enjoy larger organisation structures and staying only within your area of expertise. Taking ownership here means doing whatever the problem needs
• Want a traditional engineering team set up, with a predictable roadmap and clearly scoped out tickets provided for you
• Prefer a slower pace. Customers are depending on what we ship
• Aren't comfortable with production responsibility. We're revenue-critical infrastructure - on-call matters here

Some other cool stuff!

What our newest hires have shipped

• Watchtower: our command center for AI agents. As we introduce agents that automate financial workflows, customers need visibility and control. This included building our first agent - a contract intake system that extracts customer and pricing information from uploaded or emailed contracts, taking customers from signed contract to automated billing in minutes.

• A fully integrated e-signature experience for quotes. When a customer is closing a deal, friction kills momentum. We rebuilt the signing experience - including embedded authentication and branded emails - into a seamless signing experience used by teams at the top tech companies every day.

• Role-based access controls across the product. Different companies have different structures, but they all need tight control over who can approve deals or access sensitive data. This meant designing a flexible RBAC model that handles resources across every API endpoint and UI surface.

See more of what we’ve shipped in our public changelog.

Tech stack

We hire for ability, not a specific tech stack. Most of the team learned Kotlin here:

• Backend: Kotlin (modular monolith using Http4k, Spring Boot, Exposed, Result4k)
• Storage: Postgres, BigQuery
• Async messaging: Google Cloud Pub/Sub
• Infrastructure: Google Cloud, Terraform
• Frontend: TypeScript, React
• Monitoring: Google Cloud Monitoring, Sentry
• Tools: GitHub, Slack, Notion, Linear

Interview process

We move fast - typically 1-2 weeks start to finish:

• Initial interview (30 mins)
• Technical interview (60 mins)
• Product interview (30 mins)
• System design interview (45 mins)
• Founder interview (30 mins)

We've also written a detailed blog post about the interview process with tips about how to prepare.