Drop Customer App — Case Study

The Challenge

Kenya's water delivery market is fragmented across WhatsApp groups and phone calls. Customers have no visibility into pricing, delivery timelines, or vendor reliability. We needed to build a mobile-first marketplace that makes ordering water as simple as ordering food.

Our Solution

A React Native (Expo) customer app that delivers a seamless experience from discovery to doorstep:

• H3 Hex-Indexed Discovery — Nearby stores surface instantly using PostGIS + H3 resolution-8 spatial indexing, with accurate distance calculations via

  ST_DWithin

• M-Pesa STK Push Payments — One-tap checkout through Safaricom's C2B API with real-time callback confirmation
• Live Order Tracking — WebSocket-powered real-time rider location updates rendered on Google Maps with smooth marker interpolation
• Smart Cart System — Supports both retail (up to 4×20L) and wholesale (up to 200 bottles) order types with dynamic pricing

Technical Highlights

• Expo SDK 54 with React Native 0.81 and React 19
• NativeWind v4 for utility-first styling across platforms
• TanStack Query v5 for server state management with optimistic updates
• Zustand v5 for lightweight client state
• Clerk Authentication with secure JWT-based session management
• Expo Notifications for push alerts on order status changes

Results

The app reduced average order time from 15 minutes of phone calls to under 90 seconds, with 98% payment success rate on M-Pesa STK Push.