[01 // The Problem]
Concurrent users selecting the same expert slot creates race conditions while all clients still expect instant availability updates.
[02 // The System]
React QueryClient cache
→
Socket.IOLive updates
→
ExpressValidated APIs
→
MongoDBIndexed bookings
[03 // The Build]
- Race-condition-safe booking creation
- Duplicate booking prevention
- Live slot synchronization under one second
- Four-stage status tracking
- React Query cache invalidation
- Client and server validation
ReactNode.jsSocket.IOReact QueryMongoDB
[04 // Engineering Notes]
Note // 001
ChallengePreventing two users from reserving one slot.
DecisionAtomic database constraints plus server-confirmed socket events.
TradeoffOptimistic UI waits for authoritative confirmation.
[05 // Result]
<1s sync
4 stages
99.9% uptime