Technical Report: Wallet Functionality Implementation

• PostMan Documentation

Introduction

This report outlines the decisions and processes involved in designing and implementing the wallet functionality. The wallet system enables users to perform secure financial transactions, such as sending and receiving funds. The core setup involves a credit and debit transactions table, a controlBalance table for funds used in administrative settlement and a users table with an is_super_admin column for identifying user types.

Without affecting performance; Users balance can be calculated and retrieved anytime there's a need to get an accurate figure. To improve performance; I would cache users balance using redis for view only purposes. The choice to keep a Control Balance table for admins was made solely on the assumption that such user accounts will be handled by the right internal teams, performance improvements from having the value on a table will be minimal as it'll not be accessed often. I would always favour calculating balance based of transactions

Setting up

The env file for this project has been included in github; To aid easy setup on local machines

To run the project, Assuming php, composer, and a php server is already installed, run

• composer install
• php artisan migrate
• php artisan db:seed
• php artisan serve

Schema Design

Users Table

The users table stores user information, including authentication details and administrative status. The is_super_admin field distinguishes between regular users and administrators with enhanced capabilities. On login, tokens are generated using sanctum giving different access levels based on user type

• Columns: id, name, email, email_verified_at, password, remember_token, created_at, updated_at, is_super_admin
• Decisions: The schema includes fields necessary for user authentication and status management.

Control Balances Table

The control_balances table manages administrative funds used for initial user credits and other administrative transactions.

• Columns: id, user_id, amount, created_at, updated_at
• Decisions: Linking control_balances to users ensures traceability of administrative actions.

Transactions Tables

Separate tables for credit and debit transactions maintain a clear record of all financial activities.

• Credit Transactions: id, user_id, control_balance_id, transaction_reference, amount, description, created_at, updated_at
• Debit Transactions: id, user_id, control_balance_id, transaction_reference, amount, description, created_at, updated_at
• Decisions: Splitting transactions into credit and debit tables simplifies querying and improves performance.

Audit Logs Table

The audit_logs table records all significant actions and transactions, providing an audit trail for security and compliance.

• Columns: id, user_id, action, description, status, error, anomaly, created_at, updated_at
• Decisions: Comprehensive logging ensures accountability and facilitates troubleshooting.

Choice of Libraries and Frameworks

Laravel

Laravel was chosen for its robust ecosystem, built-in authentication, and database management capabilities. Key features utilized include Eloquent ORM, middleware, and Sanctum for API authentication.

Laravel Sanctum

Sanctum provides a simple solution for API token management and SPA authentication, ensuring secure communication with the API

Patterns for Safe Concurrency

Database Transactions

Using database transactions ensures that all operations within a transaction block either complete successfully or roll back entirely, maintaining data consistency.

• Implementation: Laravel’s DB::beginTransaction(), DB::commit(), and DB::rollBack() methods are employed to handle critical sections of the code where multiple database operations need to be atomic.

Row Locking

Row locking prevents race conditions by locking the rows being updated until the transaction completes.

• Implementation: Eloquent’s lockForUpdate() method is used to lock the user and control balance records during transaction processing, ensuring no other process can modify these records simultaneously.

Security Measures for Financial Transactions

Audit Logging

Audit logging tracks all transactions and significant actions, providing a trail that can be reviewed for suspicious activity.

• Implementation: Each transaction and action is logged in the audit_logs table with details such as user ID, action performed, status, and any anomalies detected.

Authentication and Authorization

Sanctum is used to manage API tokens and ensure that only authenticated and authorized users can perform certain transactions.

Data Encryption

Sensitive data, such as passwords, are encrypted to prevent unauthorized access.