Quarkus Real-Time Offer Service

A production-style backend service built with Quarkus (Java 21), focused on real-time offer validation and processing.

🚀 Overview

This project demonstrates how to design and implement a high-throughput backend service using modern Java and Quarkus, applying clean architecture principles and Test-Driven Development (TDD).

It is intentionally designed as a realistic microservice, not a toy example.

🧱 Architecture

• Quarkus (Java 21)
• REST APIs
• Constructor-based dependency injection
• Layered architecture (resource → service → domain)
• Centralized validation and error handling
• Isolated cache key strategy

High-Level Flow

Client
  |
  v
REST Resource
  |
  v
Service Layer
  |
  v
Domain / Business Logic
  |
  +--> Validation
  |
  +--> Cache Key Strategy
  |
  +--> Standardized Error Handling

ASCII Architecture Diagram

+-------------------+
|      Client       |
+-------------------+
          |
          v
+-------------------+
|   REST Resource   |
|  HTTP entrypoint  |
+-------------------+
          |
          v
+-------------------+
|   Service Layer   |
| orchestration/use |
|      cases        |
+-------------------+
          |
          v
+-------------------+
| Domain / Business |
|       Logic       |
+-------------------+
      /    |     \
     v     v      v
+---------+ +-------------+ +----------------------+
|Request  | | Cache Key   | | Standardized Error   |
|Validation| | Strategy    | | Handling / Responses |
+---------+ +-------------+ +----------------------+

Key Design Choices

• TDD-first approach: features start from failing tests
• No field injection: improved testability and clarity
• Standardized error responses: consistent API behavior
• Separation of concerns across layers
• Cache key isolation to avoid hidden coupling

⚙️ Tech Stack

• Java 21
• Quarkus
• JUnit 5
• Mockito
• Maven

🧪 Testing

The project follows a strict TDD approach:

• Tests are written before implementation
• Validation scenarios are explicitly tested
• Focus on behavior rather than implementation details

Run tests:

./mvnw test

▶️ Running the Application

./mvnw quarkus:dev

📌 Example Features

• Request validation with meaningful error responses
• Clean service layer abstraction
• Cache-ready architecture
• Testable and maintainable codebase

🤖 AI-Assisted Development

This project was developed using AI-assisted tools, with a strong focus on:

• Code correctness and validation
• Avoiding "AI-generated noise"
• Maintaining clean, production-quality code

All generated code was reviewed, validated, and refined through TDD.

🎯 Purpose

This repository is intended to demonstrate:

• Hands-on expertise with Quarkus
• Backend architecture skills
• Testing discipline (TDD)
• Production-oriented coding practices

🔗 Author

Menashe Eliezer
Senior Backend Engineer
LinkedIn: https://linkedin.com/in/menashe-eliezer-254267