Functional & Non-Functional Requirements

Requirements

The vending machine system must fulfill several key requirements to ensure efficient operation and user satisfaction. Firstly, it should offer a diverse range of products such as snacks, beverages, and convenience items. Each product must have associated pricing and updated inventory levels. Additionally, the system must provide a user-friendly interface for product selection, allowing customers to intuitively navigate the options.

Payment methods are crucial; therefore, the system must support various payment options including cash, credit/debit cards, and mobile payments. Security is paramount, so all transactions should be encrypted and validated. Furthermore, the system should allow for easy inventory management to track sales, restock requirements, and prevent out-of-stock scenarios.

Capacity Estimation

Estimation

The project can be broken down into several phases, including requirements gathering, system design, implementation, and testing. An initial time estimation could be around 4-6 weeks for a basic version of the vending machine system. This includes time for building a user interface, developing back-end services, integrating payment systems, and performing thorough testing.

For scaling the system, an additional 2-3 weeks may be needed to implement advanced features such as machine learning for inventory predictions or user preference tracking. The cost of hardware and maintenance should also be considered, as well as ongoing support and updates for the software.

API Design

API

The vending machine system will expose a RESTful API for frontend interactions. Key endpoints may include:

• GET /products - Retrieves a list of available products with prices and stock status.
• POST /purchase - Processes a payment and dispenses the selected product, validating payment and inventory.
• PUT /inventory - For backend management to update stock levels after a purchase or during restocking.
• GET /transactions - Fetches transaction history for analytics and reporting.

Each request will require appropriate authentication to prevent unauthorized access and ensure secure transaction processing.

Database Design

Database

The system should utilize a relational database to manage products, transactions, and user data effectively. The database schema can include tables like:

• Products: Stores product ID, name, price, and stock level.
• Transactions: Records each purchase with fields for transaction ID, product ID, amount, payment method, and timestamp.
• Users: (if applicable) maintains user profiles, including payment methods and purchase history.

This relational database design ensures that data can be efficiently queried, updated, and managed, facilitating real-time performance reporting and inventory tracking.

High Level Design

High-Level Architecture

The high-level architecture of the vending machine system consists of several key components working together. At the top layer is the user interface, which could be a touchscreen or mobile app that allows users to select products. This interface interacts with a load balancer to ensure optimized requests to backend services.

The backend services comprise payment processing modules, inventory management, and transaction logging. These services interact with a database for persistent storage of products and transactions. Instead of directly querying the database every time, a caching mechanism could be used to enhance performance and reduce latency.

Request Flows

Request Flow

The request flow in the vending machine system can be described as follows:

1. The user selects a product via the user interface.
2. The system checks the product's availability and retrieves its price.
3. The user initiates payment through their chosen method.
4. The payment processing service validates the payment and confirms the transaction.
5. If successful, the product is dispensed to the user, and inventory is updated.
6. Transaction information is logged for future analytics and reporting.

This flow ensures that each payment is synchronized with inventory management and provides users with immediate feedback.

Detailed Component Design

Components

The core components of the vending machine system include:

• User Interface: Hardware or software interface for user interaction.
• Payment Processor: Handles different payment methods and transaction validation.
• Inventory Manager: Tracks product stock levels and manages restocking processes.
• Database: Stores product information, transaction history, and user profiles.
• Analytics Service: Analyzes sales data for inventory predictions and user behavior insights.

Each of these components communicates with the others to deliver seamless operation.

Trade-offs & Tech Choices

Trade-Offs

When designing the vending machine system, various trade-offs must be considered. For instance, opting for a more complex user interface could enhance user experience but may require more development time and resources. Similarly, while providing multiple payment options improves accessibility, it also increases the potential attack surface for security vulnerabilities.

Choosing between a relational database and a NoSQL option also represents a trade-off. A relational database is beneficial for structured transactions, while NoSQL may offer more flexibility for non-structured data. The decision should be based on anticipated scale and usage patterns.

Failure Scenarios & Bottlenecks

Failure Scenarios

Several failure scenarios should be anticipated in the vending machine system. Firstly, if a payment fails due to network issues or declined cards, the user should be informed and allowed to retry. The system must ensure that inventory is not deducted until payment is successfully processed.

Another scenario could involve product malfunctions, where the machine fails to dispense the selected item. In such cases, the system should automatically notify the user and provide a refund option. Additionally, the inventory management should handle scenarios where stock levels are inaccurately reported, leading to out-of-stock products unexpectedly.

Future Improvements

Future Improvements

In the future, the vending machine system could be enhanced with features like user account integration, allowing for personalized recommendations and easier transaction histories. Additionally, machine learning algorithms could be introduced to analyze consumer behavior, optimizing stock levels and product offerings based on demand patterns.

Furthermore, IoT integration could allow for remote monitoring and alerts for maintenance and stock levels. This would ensure prompt replenishment and reduced machine downtime, thus improving the overall user experience.

High Level Architecture Diagram

Database ER Diagram

Request Flow Sequence Diagram