Integrasi Haversine, Pelacakan Real-Time, dan Payment Gateway Berbasis Idempoten pada Sistem Layanan Laundry

Conventional laundry services generally require customers to visit physical outlets and face uncertainty regarding costs and processing status. On the operational side, courier pickup-and-delivery assignment is often conducted manually without optimal route determination, fleet tracking is not centralized, and payment integration is vulnerable to duplicates caused by race conditions. This study aims to develop a multi-actor on-demand laundry service system that integrates spatial validation, real-time tracking, and secure digital transactions. The system is built using a client-server architecture comprising a Flutter mobile application for customers and couriers alongside a Laravel web dashboard for administrators, interconnected via an Application Programming Interface (API). Service radius validation (geofencing) and nearest courier allocation (auto-dispatch) are computed on the server using the Haversine formula. Real-time courier tracking is facilitated through the Firebase Realtime Database and Open Source Routing Machine (OSRM). Digital payment transactions are integrated with the Midtrans payment gateway, applying an idempotency key mechanism and database row lock to prevent double charges. The test results demonstrate that the Haversine formula successfully verifies service coverage and allocates the nearest courier, location coordinates synchronize accurately on the map, and the idempotency mechanism processes repeated requests with a 100% single-processing success rate. This system provides pricing transparency, expedites pickup workflows, and guarantees transactional data integrity.