Software Engineer — Junior / Mid in London

The role involves building the backend systems Letly runs on — the software behind every viewing, tenancy, certificate, rent payment and repair. These are systems where correctness, reliability and scale are non-negotiable: real people’s money, homes and legal exposure are on the line. This is a junior-to-mid hire. At junior level, you ship features inside services others own — with review, mentoring and real production responsibility from the first month. At mid level, you own features and services end-to-end.

What you’ll work on:

• Money movement: Rent, deposits and payouts through pooled client-money accounts — idempotent processing, split-settlement, exactly-once across service and bank boundaries.
• Reconciliation & bookings: A penny-accurate, self-healing ledger reconciling bank activity across thousands of tenancies; contended scheduling — viewings, certs, photography, maintenance against finite slots and vendor availability.
• Event-driven consistency: Services coordinating over Pub/Sub — sagas across offer contract tenancy payment with no distributed transaction to lean on. LLM tool calling, deterministic API calls, and other intra- and inter-service communications all running across the same coordination system.
• AI harnesses in production: Deploying agentic AI into real-world operational settings — acting on real money, tenancies and legal exposure, with the guardrails, observability and correctness that demands. Non-deterministic LLM working within compliant, secure deterministic software.

Our stack: We build on NestJS + TypeScript on GCP / GKE, with MongoDB, Redis and GCP Pub/Sub. You don’t need to arrive fluent in it. We hire strong backend engineers who’ve built production systems with any robust framework — Java/Spring Boot, Go, Kotlin, C#/.NET, Python (Django/FastAPI) or Ruby on Rails — and can ramp into TypeScript fast. We care that you’ve built and operated real backends, not which language you did it in.

How we build: Small, well-factored services. TDD and DDD as defaults. Trunk-based CI/CD — you ship to production and own it, with tests, observability and clean rollbacks. Lean frameworks, readable code, and we move fast because the tests and boundaries let us.

What we’re looking for:

• 0–2 years building production backend systems for junior, 3+ for mid; for junior, serious internships or shipped side projects count.
• Fluency in at least one backend language and framework, and the appetite to reason about system design rather than just the ticket.
• Strong fundamentals: concurrency, HTTP and API design, data modelling (document or relational), and what actually happens when a call fails.
• You treat tests as part of shipping, and you can read a large codebase you didn’t write.
• AI-Native engineer: you use AI across all layers of your work and utilise models expertly while understanding LLM failure modes and patterns.
• Junior: you’ve shipped code real users depended on — an internship, a placement or a substantial side project counts.
• Mid: you’ve owned a service or a substantial feature in production end-to-end.

Nice to have:

• MongoDB and GCP/GKE.
• Event-driven architecture and message brokers (Pub/Sub, Kafka).
• Exposure to payments, ledgers, reconciliation or another domain where being wrong costs money.
• A computer-science or other technical degree, or a track record that makes one irrelevant.

Who does well here:

• You’re precise about correctness — these systems move money; “mostly right” fails.
• You own the outcome, not the ticket — start to production, without being chased.
• You ask early and learn fast — the fastest engineers here are the ones who close the loop quickest.
• You want the hard problems — and you get real ones early.

Why apply: Letly is the AI-Native operating company built for the home. We believe the home will be autonomously run by AI and we’re building the software that will run all rental properties end-to-end, starting with London (the world’s 2nd largest rental city). The backend at Letly is technically difficult on purpose: messy operational reality that doesn’t fit clean schemas; money moving across financial rails where being wrong is not an option; high throughput across thousands of concurrent journeys; and a large surface serving many user types with different needs, permissions and trust levels. Early in a career that matters — you’ll work on distributed systems and money movement now, not in three years, alongside engineers who will review your code properly. We’ve raised a $4m pre-seed from investors who’ve built the financial and operational infrastructure that moves billions and serves millions. They backed us because the home is the largest consumer asset where that infrastructure hasn’t been built yet. You’ll get competitive base pay, meaningful equity, and a small, high-agency team rebuilding an industry and growing at >100% month-over-month. We’re hiring to facilitate this aggressive growth.