Senior Product Engineer (Backend) - London

Sequence

Greater London

On-site

GBP 115,000 - 130,000

Full time

14 days+

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Benefits offered by this job

Salary: £115,000 - £130,000

Equity: Meaningful share options

25 days holiday + bank holidays

Job summary

A financial technology company based in London is seeking an experienced engineer to enhance their AI-powered revenue platform. You will work on developing intelligent workflows and optimizing backend systems, driving significant impact as the company scales. Ideal candidates will have strong backend experience, familiarity with distributed systems, and a proactive approach to problem-solving. Competitive salary, equity options, and a collaborative work culture are offered.

Qualifications

Proven experience in shipping reliable backend systems.
Strong understanding of customer needs and feedback.
Ability to adapt in early project stages.

Responsibilities

Build flexible AI-powered approval workflows.
Develop an intelligent collections agent for late payments.
Redesign billing infrastructure for increased throughput.

Skills

Production backend systems experience

Clear communication

Comfort with ambiguity

Interest in distributed systems

Tools

Postgres

Google Cloud

Kotlin

Job description

About Sequence

If you join Sequence, you'll help build the platform that lets companies get paid – we’re already processing $1bn+ in annual invoice volume and growing fast. We're building the AI-powered revenue platform for modern finance teams, replacing fragile spreadsheets and legacy systems with software their teams love using. Cognition, incident.io, MoonPay, and 100+ other high-growth companies trust us to handle their entire revenue cycle across quoting, billing, and revenue recognition. Founded by repeat entrepreneurs, we hit 10x ARR growth last year and just closed a $20M Series A led by 645 Ventures, alongside a16z and exceptional founders and CFOs from companies like Decagon, Klaviyo and Wise.

What's it like to work at Sequence?

Small team, big opportunity, real ownership. You'll do work that matters, have direct access to customers, and grow alongside the company. If you want to do the best work of your career at a company that's scaling fast, we'd love to meet you.

What You'll Be Doing

We care deeply about the quality of the product we're building. We're looking for engineers who are ambitious and take ownership end-to-end: from identifying what to build, through shipping, to making sure it works for real customers.

Here’s what you might work on:

AI-powered approval workflows. Enterprise deals need approval chains, but rigid workflows break when every company has different rules. You'll build flexible routing that customers configure in natural language – “require VP approval for deals over $100k with annual terms” – and turn that into deterministic, auditable business logic.
An intelligent collections agent. Chasing late payments is tedious, manual work. We're building an agent you instruct in natural language (“send a reminder at 7 days overdue; elevate at 14 days”), which then runs the entire workflow autonomously.
Scaling billing infrastructure 10x. We’re building revenue-critical infrastructure and currently rearchitecting our billing pipeline for an order of magnitude more throughput – rethinking storage strategies, horizontal scalability, and how we’ll handle 10x load without 10x cost.

We're a lean team growing to 20+ engineers. You'll have real influence on what we build and how we build it. Early enough to shape fundamental architecture. Late enough that customers depend on what you ship. You'll design systems that process high-velocity event streams, make technical decisions that balance cost and performance at scale, and build infrastructure that never compromises on reliability. This is business-critical infrastructure: a dropped event means someone isn’t charged correctly. An outage at month-end means finance teams can't collect revenue from their customers.

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.

You should apply if

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

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.

Tech stack

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

How We Work

We’re based in London and New York and love spending as much time with our colleagues as possible. We spend three days together in the office, with team lunch on Wednesdays. You'll join a cross-functional product team working directly with design and product. We get together twice a year for company offsites.

What we offer