Requirements of PayPal

A Payment Gateway System like PayPal must handle secure, real-time transactions between users, banks, and merchants. The requirements of such a system are categorized into Functional Requirements and Non-Functional Requirements to give a complete overview of what the system should do and how it should perform.

Functional Requirements:

• User Registration and Authentication
  The system should allow users to register using a valid email address or mobile number, and create a secure password. Upon login, users should go through secure authentication, including options like two-factor authentication (2FA).

• Account Management
  Users must be able to create either personal or business accounts, update personal information, link their bank accounts, credit/debit cards, or digital wallets, and view their transaction history.

• Send and Receive Money
  The system should allow users to send money to others using email or mobile number, and receive money in their PayPal account, with the option to transfer it to a linked bank account.

• Payment to Merchants and Invoicing
  Users (especially businesses) should be able to make online payments to vendors or e-commerce platforms. It should also allow creation and sending of invoices directly from the PayPal account.

• Currency Conversion
  The system should automatically convert the currency when users transact in different countries, based on real-time exchange rates and applicable service charges.

• Dispute Resolution & Refunds
  A built-in resolution center should exist where users can raise disputes for unreceived items or fraud. The system must also allow for partial or full refunds of transactions.

Non-Functional Requirements:

• Security and Compliance
  The system must comply with PCI-DSS standards, SSL encryption for all communications, and implement fraud detection algorithms to safeguard user data and funds.

• Performance and Scalability
  The application should be able to handle thousands of concurrent transactions without lag, ensuring minimal downtime even during peak traffic.

• Availability and Reliability
  The system should ensure high availability (ideally 99.999%) with backup systems and recovery protocols to prevent transaction loss in case of system failure.

• Audit and Logging
  Every action (like login, money transfer, refund) should be logged for auditing purposes. This is crucial for debugging, legal compliance, and preventing financial misuse.

• Platform Compatibility
  PayPal must be accessible via web browsers, mobile apps (Android/iOS), and API integrations with third-party platforms such as e-commerce websites and point-of-sale systems.

• User Interface and Experience (UI/UX)
  The interface should be intuitive, responsive, and user-friendly for all types of users, providing accessibility support and multi-language options where applicable.