SimplePay - PicPay Backend Challenge

This project is a submission for the PicPay Backend Technical Challenge.
It implements a simplified payment platform backend inspired by PicPay’s requirements, developed with Java Spring Boot following Clean Architecture principles.

About the Challenge

The goal was to build a system where users and merchants can manage wallets and transfer money securely, respecting business rules such as:

• Unique CPF and email per user.
• Two user types: Regular Users and Merchants.
• Merchants can only receive transfers, not send.
• Transfers require balance validation and external authorization.
• Notifications sent through external mock service.
• Transactional consistency on transfers.

Features

• User registration with validations.
• Wallet and balance management.
• Secure transfer flow with external authorization and notification mocks.
• Clean Architecture for maintainability and testability.
• RESTful API endpoints.

Technologies Used

• Java 17+
• Spring Boot 3.x
• Spring Data JPA (Hibernate)
• PostgreSQL (or any relational DB)
• Maven

Architecture Overview

The project is structured into layers respecting Clean Architecture:

• Domain: Business entities and rules.
• Application: Use cases and service logic.
• Infrastructure: Database, external API clients.
• Interface: REST controllers exposing the API.