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Similar Products API

REST API implementation with Spring Boot 4.0.1 and Java 17 that exposes an endpoint to retrieve similar products with their details.

Architecture

Client → Controller → Service → ApiClient → Mock APIs

Main components:

  • Controller: REST endpoint GET /product/{productId}/similar
  • Service: Business logic with parallel HTTP calls
  • ApiClient: HTTP client with configured timeouts
  • Model: DTOs (ProductDetail)
  • Exception Handling: Global error handling (404)

Evaluation criteria

1. Code Clarity and Maintainability

Clean and organized architecture:

  • Separation of concerns (Controller, Service, Client, Config)
  • Constructor-based dependency injection
  • Descriptive names and self-documenting code
  • Centralized exception handling with @RestControllerAdvice

2. Performance

Implemented optimizations:

Parallel HTTP calls:

  • Using CompletableFuture with ForkJoinPool of 50 threads
  • Instead of N sequential calls, all are executed in parallel
  • 25-40% improvement in scenarios with multiple similar products
  • 3x improvement in high-latency scenarios (1-5 second delays)

Configured timeouts:

  • Connect timeout: 2 seconds
  • Read timeout: 5 seconds
  • Prevents indefinite blocking

K6 test results (200 concurrent VUs):

  • 116 requests/second
  • P90: 149ms
  • P95: 378ms

3. Resilience

Implemented strategies:

  • Timeouts: Prevents infinite waits on HTTP calls
  • Robust error handling:
    • Returns 404 when main product does not exist
    • Filters similar products that cannot be obtained without breaking the flow
  • Robust HTTP client: Spring RestClient with error handling
  • Controlled thread pool: 50 thread limit for I/O operations

Project structure

src/main/java/com/backendtest/similarProducts/
├── SimilarProductsApplication.java
├── client/
│   └── ProductApiClient.java
├── config/
│   └── RestClientConfig.java
├── controller/
│   └── SimilarProductsController.java
├── exception/
│   ├── GlobalExceptionHandler.java
│   └── ProductNotFoundException.java
├── model/
│   └── ProductDetail.java
└── service/
    └── SimilarProductsService.java

Execution

Option 1 - Docker Compose (recommended):

docker-compose up -d --build
docker-compose run --rm k6 run scripts/test.js

View results: http://localhost:3000/d/Le2Ku9NMk/k6-performance-test

Option 2 - Local:

docker-compose up -d simulado influxdb grafana
./mvnw spring-boot:run
curl http://localhost:8080/product/1/similar

API

GET /product/{productId}/similar

Returns the details of similar products for a given product.

Successful response (200):

[
  {
    "id": "2",
    "name": "Product 2",
    "price": 29.99,
    "availability": true
  }
]

Product not found (404):

HTTP/1.1 404 Not Found

Technologies

  • Spring Boot 4.0.1
  • Java 17
  • RestClient (Spring 6.x)
  • Maven 3.9.6
  • Docker and Docker Compose
  • K6 for load testing
  • Grafana and InfluxDB for metrics

Technical notes

Port 8080: Port 5000 is occupied by AirPlay Receiver on macOS Monterey and later versions.

Parallelization: HTTP calls to similar products are executed in parallel using CompletableFuture with ForkJoinPool, optimized for I/O operations.

Error handling: If the main product does not exist, returns 404. If any similar product cannot be obtained, it is filtered from the response without breaking the flow.