Developer

Role & responsibilities

About the role
Arcus is a software platform for UK fire alarm installation and maintenance companies, covering everything from designing a system to quoting, installing, certifying and maintaining it. Were hiring a Full Stack Developer to take the product from a strong demo to something contractors run their business on every day. You’ll work closely with our ML Engineer and ship features end to end, from database and APIs through to the screens people use in the office and on site.

Responsibilities

• Integrate our AI detection pipeline into the app with the ML Engineer, running detection as background jobs, storing results against model versions and showing confidence so designers know what to check
• Build a feedback loop that turns designer corrections into labelled training data
• Build interactive canvas tools in Konva for reviewing rooms, placing devices, drawing walls and calibrating scale
• Build and extend modules across the full job lifecycle, including clients, properties, designs, quotes, jobs, timesheets, compliance, assets and invoicing
• Build AI-assisted job scheduling that suggests the right engineer, date and route for each job, with a scheduler confirming every booking
• Build field service apps on mobile web and native, with job sheets, defect photos, customer signatures and offline working that syncs later
• Move modules from sample data onto PostgreSQL using TypeORM, without breaking existing screens
• Design versioned APIs used by the web app, mobile apps and ML services
• Generate compliant documents such as certificates, quotes and invoices that print correctly
• Write tests alongside your code and keep the test suite healthy

Preferred candidate profile

Must have

• 5+ years building production web applications in TypeScript, with strong React experience
• Hands-on experience with Next.js App Router, including server components, server actions and caching
• Confident designing PostgreSQL schemas and working through an ORM, including migrations and query performance
• Experience putting ML models into a real product, using background jobs, queues and versioned outputs
• Experience building mobile apps in React Native or as a production PWA, including offline storage and sync
• Working Python, enough to read, debug and extend a FastAPI service
• Writes tests first or alongside code, at both unit and browser level
• Experience with authentication, user roles and server-side permissions
• Good eye for UI detail, accessibility and layouts that work well on a phone
• Clear written English, able to explain trade-offs in pull requests and write docs non-developers can follow

Nice to have

• Computer vision with OpenCV, or geometry work with polygons and vector data
• Experience with LLM APIs, especially vision models and structured output
• Scheduling or route optimisation experience
• Publishing apps to the App Store and Google Play
• Maps, geolocation and routing APIs
• Canvas or diagramming tools such as Konva or Fabric
• Background in field service, job management or ERP software
• Familiarity with audit trails and UK GDPR