Transactional / OOD• Patterns: Strategy, Observer

Inventory System

Hard

Problem Summary

Design a warehouse inventory system tracking stock levels, processing order picks, and alerting low stock events.

Functional Scope

Track quantities of products across different warehouse layouts.
Reserve stock immediately during checkout.
Trigger notifications to suppliers once inventory falls below a threshold.

Entity-Relationship (ER) Schema

Warehouse [1] <---> [*] InventoryItem
InventoryItem [1] <---> [1] StockLevel
Order [1] <---> [*] OrderItem

Design Approach

Apply pessimistic locks to individual inventory SKU rows to prevent transaction race conditions during popular flash sales.

Core Classes & Models

ProductItem (Item details, sku)StockLevel (Quantity available, reserved counts)Order (List of items, packing status)Warehouse (Locations, replenishment policy)

Code Blueprint

public class InventoryItem {
    private int quantity;
    public synchronized boolean reserve(int count) { return true; }
}