Back End Developer

Senior / Staff Backend Engineer £136k–£180k + equity | Remote Europe or London

I’m working with a Series A developer infrastructure startup on one of the more technically demanding backend roles I’ve come across this year.

The platform runs AI agents and background workflows in production, at massive scale. Some customers execute hundreds of millions of jobs per month. The team is ~20 people, there are no engineering managers, and engineers own large parts of the system while working directly with the founders on architecture. The product is also open source, so the work you do here doesn’t disappear into a private codebase. It’s reviewed in the open, used by thousands of other engineering teams, and becomes part of your own public track record, not just a line on a CV.

The core challenge right now is infrastructure scale. Execution volume is growing faster than the team can build, which means the next hires are walking into a genuine distributed systems problem, not a greenfield rebuild or a dashboard feature.

What the role actually involves

• Scaling infrastructure that handles millions to billions of agent workflow executions a month
• Keeping systems reliable under extreme concurrency and sudden load spikes
• Building secure, isolated execution environments for user-submitted code (Firecracker micro-VMs)
• Managing server lifecycle, spinning capacity up and down fast as load shifts
• Building out observability and reliability tooling across the stack
• Working in the open, with code reviewed by and visible to the wider developer community

The stack

• TypeScript (99% of the codebase)
• PostgreSQL, Redis, ClickHouse
• Kubernetes background useful (they’re evolving away from it, but the mindset matters)

What they’re looking for

• Backend engineers who’ve operated systems at serious scale, fintech, devtools, or infrastructure-heavy SaaS
• Deep understanding of distributed systems, reliability, and infrastructure design
• Comfortable owning large surface areas with minimal direction
• Engineers who use AI tooling heavily, this is screened for directly in the interview
• High intrinsic motivation, the team moves fast and doesn’t slow down for anyone

What they’re not looking for

• Full-stack engineers whose instinct is to reach for the frontend
• Anyone who needs structured management to ship
• Candidates coming from large enterprises or low-velocity environments

Comp

• Senior: £136k–£150k + ~0.3% equity
• Staff: £164k–£180k + ~0.3% equity

The bar’s genuinely high, and it can be as this is one of the most popular clients and roles we have so if you’ve built backend systems at this kind of scale, apply or message me (Sam Barcia)