← Work Duurzame Bouwkeet · 2024 · Freelance Full Stack Developer

After a series of demos to major Dutch enterprises, the app is now live in offices at Schiphol Airport and KWS.

1// device state arrives as events, never polled2const ws = new WebSocket(DEVICE_URL);3ws.onmessage = ({ data }) => {4  const msg = JSON.parse(data);5  if (msg.type === 'energy') supply.set(msg.watts);6  if (msg.type === 'device') devices.update(msg.id, msg.state);7};

src/lib/live.ts

Duurzame Bouwkeet builds off-grid and CO₂-neutral construction site offices for major Dutch enterprises. Their clients needed to control climate, lighting, and connected devices from a compact wall-mounted touchscreen — no keyboard, no technical knowledge assumed, running entirely on-device.

Year: 2024
Role: Freelance Full Stack Developer
Stack: Svelte · TypeScript · Node.js · WebSockets
Live: duurzamebouwkeet.nl ↗

Approach

I was brought in as a freelance developer to build the frontend from scratch. Bundle size mattered here: the app runs directly on the touchscreen hardware, so I chose Svelte for its minimal runtime footprint and gentle learning curve — keeping the app fast on constrained hardware while ensuring any future developer could maintain it without friction. Real-time energy supply data and device state had to update instantly, which made WebSockets the only real option over the Node.js backend. Rather than polling, device changes are triggered via events — immediate feedback in a context where delayed response would feel broken.

Solution

The biggest design challenge was serving two audiences in one interface. Workers needed a clean, distraction-free view for daily use. Admins needed access to device logs and system diagnostics. I designed both modes within a single interface, keeping the context switch invisible to everyday users.

Outcome

After a series of demos to major Dutch enterprises, the app is now live in offices at Schiphol Airport and KWS.