Case study
JBH International Limited
B2B multi-vendor marketplace for garment products — live on Google Play with concurrency-safe inventory.
2023 · Mobile engineer — React Native app & inventory correctness
- React Native
- Expo
- Supabase
Problem
A B2B garment marketplace needed advanced search and filtering across product categories, smooth performance on low-end Android devices, and correct stock counts when many buyers hit checkout at once.
Approach
Shipped a React Native (Expo) client backed by Supabase. Tuned list rendering and queries for constrained devices. Fixed a concurrency/race-condition bug in the stock-update flow that caused negative inventory and overselling during high-traffic checkout — resolved with database transactions and pessimistic row-level locking (FOR UPDATE).
Architecture
- React Native + Expo client for cross-platform mobile delivery
- Supabase-backed data and auth for marketplace operations
- Advanced search and filtering across garment product categories
- Pessimistic row-level locking (FOR UPDATE) inside transactions for stock updates
- Performance work targeting low-end Android devices
- Google Play distribution with ongoing active daily users
Outcomes
- Verified with 20 concurrent purchases against a 1-unit product — 0 units oversold
- Published on Google Play Store with 2,050+ downloads and active daily users
- Proven ability to ship production mobile clients and fix concurrency bugs under load