Software Engineer

About DolfinWe're building the agentic financial ops API for SMB platforms. Fintechs, vertical SaaS, banks, and PSPs use Dolfin to embed AI-native financial ops agents (invoicing, bills, expenses etc) directly into their products. White-label, API-first, production-ready.Our agents live in production with real SMBs. We're live and moving fast: signed platform clients including a unicorn, pipeline in the $M's, and part of Balderton's latest 'Launched' cohort.We're looking for a Senior Backend Engineer to build the core of the platform alongside the founding team. This is a deep, heads-down build role: design and ship the systems everything else runs on, and own them in production.What you'll be doingDesign, build, and own core backend services, APIs, and infrastructure.Build the event-driven, multi-tenant systems partners embed into their products.Ship LLM and agentic workflows into production, where correctness and reliability actually matter.Own the hard parts: data models, state machines, failure modes, audibility, performance.Take features from spec to production and stand behind them once live.Partner directly with the founders on architecture and technical trade-offs.How we buildProduction-first. If it isn't live and reliable, it isn't done.Correctness is non-negotiable - reliability, auditability, and failure modes come first.Pragmatic, not dogmatic. Boring tech where it counts, bold choices only where they differentiate.AI-native. LLMs as infrastructure, not features.Built to embed. API-first and multi-tenant from the ground up.Small team, high trust. Judgement over process, every time.What you'll need4+ years shipping and owning production backend systems.A fintech background is essential - ideally fintech API infrastructure (payments, ledgers,. accounting, banking, open finance). You've built or integrated financial APIs and understand what breaks.Deep experience with event-driven, multi-tenant backends and the correctness demands of money movement.Genuinely autonomous: take an ambiguous problem, make the call, ship it.Comfortable operating without structure, and creating it.Able to jump into frontend when a feature genuinely needs it.Bonus: hands-on with LLMs/agentic systems, payment or open-banking integrations (Stripe, Yapily), or time at an API-led fintech (Codat, TrueLayer, GoCardless, Modulr).Who this is forEngineers who want to go deep on hard backend problems. Builders who've shipped zero-to-one and owned it in production. People who make the call rather than wait to be told.Not for: fully remote candidates, big-company pace, or anyone who needs tightly scoped tickets.Why usGenuine early-team role with meaningful equity.Real production AI systems, not experiments.Deep ownership of the systems the whole product runs on, and a hand in shaping the architecture and engineering culture from day one.Southbank, London, in-person. Full-time. Let's go!