How to Boost Spring Boot Performance by 100x using Redis Cache

In this tutorial, we will take a "Slow API" (that takes 3 seconds to load) and turn it into a "Fast API" (that loads in milliseconds) using Redis Caching.

Tutorial Description

We will simulate a product database. When a user asks for product details, it simulates a slow database query. We will then implement Redis to store this result in memory so that subsequent requests are instant.

Tools and Technologies

Java 21
Spring Boot 3.5.x
Redis (The most popular in-memory data store)
Docker (To run Redis)

Development Steps

Step 1: Run Redis using Docker
Step 2: Add Dependencies
Step 3: Configure Redis and Enable Caching
Step 4: Create the Service (The "Slow" Logic)
How to Test This? (The "Wow" Factor)

1. Step 1: Run Redis using Docker

Instead of installing Redis manually, we use Docker. Create a docker-compose.yml file.

1. File: docker-compose.yml

Run docker: docker-compose up -d

Code Example

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services:  redis:    image: redis:alpine    container_name: practice-redis    ports:      - "6379:6379"

2. Step 2: Add Dependencies (File: build.gradle)

We need the Spring Data Redis starter.

Code Example

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dependencies {    implementation 'org.springframework.boot:spring-boot-starter-web'    // The core dependency for Caching + Redis    implementation 'org.springframework.boot:spring-boot-starter-data-redis'        compileOnly 'org.projectlombok:lombok'    annotationProcessor 'org.projectlombok:lombok'}

2. Step 3: Configure Redis and Enable Caching

We need to tell Spring Boot where Redis is running and explicitly turn on the caching feature using @EnableCaching.

1. File: src/main/resources/application.properties

Code Example

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spring.application.name=RedisCacheDemo​# Redis Configurationspring.data.redis.host=localhostspring.data.redis.port=6379

2. File: src/main/java/com/planetlearning/cache/CacheApplication.java

Code Example

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package com.planetlearning.cache;​import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cache.annotation.EnableCaching;​@SpringBootApplication@EnableCaching // <--- IMPORTANT: This turns on the magic!public class CacheApplication {    public static void main(String[] args) {        SpringApplication.run(CacheApplication.class, args);    }}

3. Step 4: Create the Service (The "Slow" Logic)

We will create a service that simulates a slow database call using Thread.sleep(). We use the @Cacheable annotation to fix it.

1. File: src/main/java/com/planetlearning/cache/service/ProductService.java

Code Example

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package com.planetlearning.cache.service;​import org.springframework.cache.annotation.CacheEvict;import org.springframework.cache.annotation.Cacheable;import org.springframework.stereotype.Service;import java.io.Serializable;​// A simple DTO (Must implement Serializable for Redis!)record Product(String id, String name, double price) implements Serializable {}​@Servicepublic class ProductService {​    // 1. @Cacheable: If data is in Redis, return it. If not, run method and save to Redis.    @Cacheable(value = "products", key = "#id")    public Product getProductById(String id) {        simulateSlowDatabase();        return new Product(id, "Iphone 15 Pro", 999.99);    }​    // 2. @CacheEvict: When we update data, we MUST clear the old cache!    @CacheEvict(value = "products", key = "#id")    public String updateProduct(String id, double newPrice) {        return "Product updated! Cache cleared.";    }​    // Simulates a 3-second database delay    private void simulateSlowDatabase() {        try {            long time = 3000L;            System.out.println("Going to sleep for " + time + " ms to simulate DB call...");            Thread.sleep(time);        } catch (InterruptedException e) {            throw new IllegalStateException(e);        }    }}

4. Step 5: The Controller

Expose the endpoints to test the speed.

1. File: src/main/java/com/planetlearning/cache/controller/ProductController.java

Code Example

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package com.planetlearning.cache.controller;​import com.planetlearning.cache.service.ProductService;import com.planetlearning.cache.service.Product;import org.springframework.web.bind.annotation.*;​@RestController@RequestMapping("/api/products")public class ProductController {​    private final ProductService productService;​    public ProductController(ProductService productService) {        this.productService = productService;    }​    @GetMapping("/{id}")    public Product getProduct(@PathVariable String id) {        return productService.getProductById(id);    }​    @PutMapping("/{id}")    public String updateProduct(@PathVariable String id, @RequestParam double price) {        return productService.updateProduct(id, price);    }}

5. How to Test This? (The "Wow" Factor)

First Request (The Slow One):
- ```
Call GET http://localhost:8080/api/products/1
```
- Result: You will wait 3 seconds. The console will print: "Going to sleep..."
- Why? The cache was empty, so it ran the code.
Second Request (The Fast One):
- ```
Call GET http://localhost:8080/api/products/1 again.
```
- Result: It returns Instantly (2ms). The console prints NOTHING.
- Why? Spring Boot fetched the result directly from Redis and skipped the Java code entirely.
Update Data (Cache Eviction):
- ```
Call PUT http://localhost:8080/api/products/1?price=1000
```
- Why? This triggers @CacheEvict, which deletes the old data from Redis so the user doesn't see old prices.

Why learn this?

In a real job, if a page is loading slowly, your boss will ask you to fix it. This tutorial teaches you exactly how to solve that problem in 10 minutes.

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