Metro transit
smart locker networks.

1. Project Context & Industry Background

Metropolitan cities support high-density commuter traffic. Rapid transit operators (such as metro rail corporations and public bus transit authorities) handle millions of passenger journeys daily. A major operational need for travelers is secure baggage storage at key transport hubs. For example, business commuters often require storage space between meetings, and tourists need temporary lockers for luggage before hotel check-in.

Traditional storage solutions utilized mechanical keys and paper tickets, requiring constant staff administration. This led to high operating costs, key loss delays, and security tracking gaps. Furthermore, anonymous cash collections created potential security liabilities. The new platform needed to enforce verified identities via mobile OTP validation, while securing all operations under a centralized cloud dashboard.

2. Operational Challenges

Deploying a keyless digital locker system inside busy train stations introduced several challenges:

• Commuter UI Simplicity: Commuters are in a rush. The booking and locker release flow had to be completed in less than 30 seconds at the touchscreen terminal.
• Network Drop Resilience: Underground metro stations have spotty internet connectivity. The local kiosk software had to validate credentials offline to ensure commuters could retrieve items during outages.
• Hardware Reliability: Lock solenoids and feedback sensors operate in high-vibration environments and require constant monitoring to detect open doors or lock failures.
• Cashless Payment Sync: The platform had to support dynamic UPI QR code scanning and reconcile payments before releasing the lock solenoids.

3. Technical Architecture & Distributed System

Hedonist Solutions engineered a distributed platform (React Web Kiosks, React Native Mobile, FastAPI API, and MongoDB):

// Asynchronous FastAPI & MongoDB Core

The backend utilizes Python FastAPI to manage asynchronous API connections from kiosks and mobile devices. We selected MongoDB to store sites, lockers, bookings, and audit records, optimizing query response times under load.

// Mobile-Kiosk Integration & Secure QR Access

Commuters can pre-book via the React Native Expo app (supporting English and Hindi) using mobile OTP authentication. The app generates a dynamic transaction token containing a secure SHA-256 hash matching the booking:

At the station, the user scans this QR code at the React Web kiosk interface, which utilizes an integrated webcam scanner to trigger locker release.

// AWS IoT Core MQTT Solenoid Relays

Each physical locker block contains custom PCB controllers connected to electromagnetic solenoid lock relays. When a scan is validated, the server publishes an activation command via AWS IoT Core MQTT. The local controller decodes the signal, triggers the solenoid, and monitors the door sensor state to transition the transaction logs through the lifecycle (booked → dropped → released).

4. Results & Impact