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Yape Code Challenge

This microservice handles the management of financial transactions, integrating asynchronous anti-fraud validation through an event-driven flow. The solution has been designed with a pragmatic and scalable approach, prioritizing data consistency and high performance in service-to-service communication.

Tech Stack

  • Java 17 / Spring Boot 4.0.3: Leveraging the latest performance improvements.
  • GraphQL (Spring GraphQL): For a flexible and optimized API that prevents over-fetching.
  • PostgreSQL 14: Robust relational persistence.
  • Apache Kafka: Event bus for asynchronous and decoupled communication.
  • MapStruct: High-performance object mapping (based on code generation, not reflection).
  • Docker & Docker Compose: Complete infrastructure orchestration.

Engineering & Design Decisions

1. Pragmatic Layered Architecture

A clear separation between Controller, Service, and Repository was implemented.

  • Justification: For this specific domain, priority was given to reducing latency and code simplicity (KISS), avoiding excessive boilerplate while maintaining solid decoupling through Mappers and DTOs.

2. Distributed Identity (Native UUID)

The Transaction entity uses a UUID as a natively generated primary key.

  • Scalability: As a system designed for High Volume, using UUIDs avoids database contention caused by traditional sequences and facilitates future horizontal scaling.
  • Data Type: The native Postgres UUID type is used to optimize storage and indexing.

3. Persistence & Event Strategy

  • Atomicity: saveAndFlush is used in the service to ensure the transaction is physically persisted before emitting the Kafka event.
  • Asynchrony: The main flow is non-blocking. The transaction is created in a PENDING state, and the final state (APPROVED/REJECTED) is updated eventually by the Kafka consumer.

How to Run the Project

Prerequisites

  • Docker and Docker Compose installed.

Steps

  1. Start infrastructure and microservices: From the repository root, run: 
    docker-compose up --build -d
    This command will spin up PostgreSQL, Kafka, Zookeeper, the Transaction Service, and the Anti-fraud Service.

API Reference (GraphQL)

Create Transaction (Mutation)

mutation {
  createTransaction(request: {
    accountExternalIdDebit: "550e8400-e29b-41d4-a716-446655440000",
    accountExternalIdCredit: "6ba7b810-9dad-11d1-80b4-00c04fd430c8",
    transferTypeId: 1,
    value: 120.50
  }) {
    transactionExternalId
    transactionStatus {
      name
    }
    createdAt
  }
}

Get Transaction (Query)

query {
  getTransaction(id: "YOUR_TRANSACTION_UUID") {
    transactionExternalId
    value
    transactionStatus {
      name
    }
    transactionType {
      name
    }
    createdAt
  }
}