ZK Training is a full management platform for a gym — one web app for staff, plus native companion apps for members on iOS (Swift) and Android (Kotlin).
Scope
- Staff web app — members, subscriptions, check-ins, scheduling, and billing.
- Member apps — native iOS and Android clients for booking, profiles, and access.
- Shared backend — a single Supabase/Postgres source of truth feeding all three clients.
Why three clients
Members live on their phones, staff live at a desk. Rather than force a compromised responsive web app on everyone, I built native where it mattered and web where density and speed mattered. The interesting engineering was keeping one backend honest across three very different surfaces — consistent auth, consistent data, no drift.