Senior Backend Engineer

About the role

Our backend work is mostly systems where being wrong costs money: payment rails that must reconcile to the cent, messaging platforms measured per unit at hundreds of millions a month, and clinical systems where the audit log is the product. The interesting problems here are the ones that only appear under load, on the worst day, when a third party is misbehaving.

What you will do

• Design and build services that stay correct under retry, partition and duplicate delivery.
• Own a system in production, including the alerting, the runbook and the 2am definition of what is worth waking up for.
• Work on legacy modernisation: characterise what exists, cover it with tests, then replace it in slices.
• Take part in red-team week, trying to break something a colleague built.
• Mentor, review and be reviewed.

What we need from you

• Years of production backend work in a typed or disciplined language, and comfort in SQL.
• You can explain idempotency to a client without using the word until the second sentence.
• Experience with a system that had real consequences when it failed.
• You write tests first on the parts that matter and can say why those parts.

Useful but not required

• Payments, telecom or clinical systems experience.
• You have run a migration that could not have downtime.
• Familiarity with event-driven architectures and their failure modes.