Offline-first: a field SaaS for electricians with no signal

Two Swiss electrical-inspection experts came to me with an idea: the tools their trade uses to inspect and certify electrical installations are clunky, paper-heavy, and never built for the field. They wanted a proper SaaS - a web back-office, a mobile app for electricians on site, and the API behind both. I have been building it with them since early 2026, and it is now heading to production.

The catch, and the best idea in the whole project, came from them: electricians work on construction sites with no signal. No 4G, no Wi-Fi. So the mobile app had to work fully offline and sync later. That single constraint shaped the entire architecture.

What the product does

It is a multi-tenant SaaS for electrical-inspection companies. Each company manages its own sites, teams, and measurement devices, fully isolated from the others. The domain runs deep:

• Sites, installations, electrical panels, circuits, measurements - the full hierarchy an electrician works through on site.
• Visual inspection and measurement workflow - a guided, step-by-step protocol (information, panels, visual inspection, measurements, manager validation) so nothing is missed.
• Control reports with AI defect extraction - an external inspector delivers a PDF report of anomalies; the manager uploads it, and an AI layer extracts the defects into the system so the electrician can resolve each one on mobile.
• PDF generation of the inspection protocols and defect-resolution notices (ASD), stored securely and shared via signed links.
• Electronic signature and locking - once signed, a protocol is locked and certified with the signer’s identity and an exact timestamp.
• Stripe billing (tiered plans and paid seats), Firebase authentication, and Swiss data residency - everything hosted in Zurich, in four languages (French, German, Italian, English).

The hard part: offline-first, done properly

Making an app “work offline” is easy to say and hard to get right, because the data is deeply nested. On site, an electrician might create a whole chain with no connection:

The server owns all the real identifiers, so offline I assign each new entity a temporary ID and show it immediately (optimistic UI) while queuing the operation in a local outbox. The moment the network comes back, a sync engine replays the queue in order, swaps every temporary ID for the real one the server returns, and reconciles the chain - even when a child was created before its parent existed on the server. Reads are persisted too, so everything opened online stays available offline, and a banner shows exactly how many actions are waiting to sync.

The result: an electrician can spend a full day on a site with no signal, do all their work, and it all lands correctly the moment they get back to coverage. No lost data, no re-entry.

How we work together

I am remote, they are in Switzerland, and it has not slowed us down. Every week they explain the trade in detail, I ship, they test with real field scenarios, and we correct and iterate - week after week, for months. That tight loop is why the product goes far beyond a generic inspection tool: the AI defect extraction, the ASD generation, the offline chain, the device-calibration tracking - all of it came out of real conversations with people who do the job.

I also help them beyond the code: setting up their App Store and Google Play accounts, and getting the mobile app through store distribution. It is a full partnership, and it is not finished.

Why it matters for you

This is what a senior engineer who owns the whole stack looks like in practice: one person taking an idea from two domain experts to a real, multi-platform product in production - web, mobile, API, infrastructure, payments, and the genuinely hard parts like offline-first done right.

Have a product idea that needs building for real - especially one with a hard technical core? Book a free 30-minute call and let’s talk through it.