A robust, high-performance Spring Boot application that provides currency exchange rates using a layered architecture with:

• ✅ External API for real-time exchange rates
• 🧠 Redis Cache for fast, short-term storage and minimizing API usage
• 🗃 PostgreSQL Database for persistence and historical lookup
• 📨 RabbitMQ for asynchronous database persistence
• 📘 Swagger UI for API documentation and testing
• 🐳 Docker Compose for seamless local development

• Get exchange rate between two currencies.
• Smart caching with Redis to avoid redundant API calls.
• Asynchronous writes to the database via RabbitMQ for improved performance.
• API-first design with Swagger documentation.
• Secure endpoints using JWT.
• Dockerized setup for Postgres, Redis, RabbitMQ, and the Spring Boot app.

graph TD
    A["Client Request (base=USD, target=EUR)"] --> B["ExchangeRateController"]
    B --> C{"Redis Cache (USD→EUR)"}
    C -- Hit --> R1["Return Cached Rate (USD→EUR)"]
    C -- Miss --> D{"Postgres DB (USD→EUR)"}
    D -- Found --> R2["Return DB Rate (USD→EUR)"]
    D -- Not Found --> E["External Exchange API Call (USD→All)"]
    E --> F["ExchangeRate Map (USD → {EUR, GBP, JPY...})"]
    F --> G["Cache All Exchange Rates in Redis"]
    G --> H["Return Requested Pair (USD→EUR) to User"]
    G --> I["Send Full Map to RabbitMQ"]
    I --> J["ExchangeRateListener"]
    J --> K["Persist All Exchange Rates to PostgreSQL"]

• Docker & Docker Compose
• Java 21
• Maven
• Free key from https://exchangerate.host/

Clone the project:

git clone https://github.com/nikossyr/CurrencyXRatesRedisRabbitMQ.git
cd CurrencyXRatesRedisRabbitMQ

Create a .env file based on .env.example provided. Add the key provided from https://exchangerate.host/ and generate a strong 512bit base64 key for HS512 encryption for JWT using the following command:

openssl rand -base64 64

Package the app to a jar using maven:

mvn package

Run all required services:

docker-compose up --build

This will start:

• Spring Boot App on localhost:8080
• Redis on localhost:6379
• PostgreSQL on localhost:5432
• RabbitMQ on:
  • AMQP: localhost:5672
  • Management UI: http://localhost:15672 (default user/pass: guest/guest)

Access Swagger UI at:

http://localhost:8080/swagger-ui/index.html

Signup with a new user using:

• POST /api/auth/signup

Login with the user created:

• POST /api/auth/login

Copy the JWT provided and add it to the Authorize button of the Swagger UI.

Now you can test the endpoint of the app:

• GET /api/exchange?base=USD&target=EUR

• 🔁 Redis: Reduces redundant external API calls using TTL-based cache.
• 💾 PostgreSQL: Stores historical and persistent data.
• ⚡ RabbitMQ: Asynchronous message queue used to save data to DB in the background.
• 🧪 Unit Tested: Service layer tested with mocks for Redis, DB, and external API.
• 🔐 JWT Ready: Token-based authentication support included
• 🐳 One-Command Setup: Fully containerized development environment.