Spring Data Redis

Introduction

Spring Boot 3 auto-configures Lettuce connection factory, RedisTemplate, and cache abstraction when spring.data.redis.* properties are set — standardizing serialization, pooling, and health indicators across microservices.

Lettuce is async and thread-safe by default; share one connection factory bean per app. Configure timeout, SSL, and cluster/sentinel via properties or RedisConfiguration beans.

Wrong serializer causes ClassCastException in prod — define StringRedisTemplate for plain text and Jackson2JsonRedisSerializer consciously for objects.

Understanding the topic

Key concepts

• spring-boot-starter-data-redis dependency.
• LettuceConnectionFactory — thread-safe shared.
• RedisTemplate generic operations API.
• StringRedisTemplate — String keys/values.
• @EnableRedisRepositories optional.
• Actuator health redis indicator.

flowchart LR
  Controller --> Service
  Service --> RedisTemplate
  RedisTemplate --> Redis

Step-by-step explanation

1. Boot reads spring.data.redis.host/port/ssl.
2. Auto-config creates ConnectionFactory bean.
3. RedisTemplate wired with default serializers.
4. Service injects RedisTemplate or StringRedisTemplate.
5. Cache abstraction uses RedisCacheManager when enabled.

Syntax reference

Common commands

• Pool max-active sized to pod concurrency.
• Use spring.data.redis.cluster for Cluster.
• Custom beans override auto-config.

# application.yml
spring:
  data:
    redis:
      host: redis.internal
      port: 6379
      password: ${REDIS_PASSWORD}
      ssl:
        enabled: true
      lettuce:
        pool:
          max-active: 16

Informative example

Minimal Spring Boot 3 configuration with typed template:

@Configuration
public class RedisConfig {
    @Bean
    StringRedisTemplate stringRedisTemplate(RedisConnectionFactory factory) {
        return new StringRedisTemplate(factory);
    }

    @Bean
    RedisTemplate<String, Product> productRedisTemplate(RedisConnectionFactory factory) {
        RedisTemplate<String, Product> t = new RedisTemplate<>();
        t.setConnectionFactory(factory);
        t.setKeySerializer(new StringRedisSerializer());
        t.setValueSerializer(new Jackson2JsonRedisSerializer<>(Product.class));
        t.afterPropertiesSet();
        return t;
    }
}

Java 21 records work with Jackson serializer. Register modules for Java time types.

Real-world use

Real-world use cases

• Standard Redis access layer in Spring microservices.
• Centralized serializer configuration.
• Sentinel/Cluster via properties.
• Health check in Kubernetes probes.
• Integration tests with Testcontainers Redis.

Best practices

• One ConnectionFactory singleton per app.
• Explicit serializers per template bean.
• Externalize secrets via env/vault.
• Enable SSL for managed Redis.
• Testcontainers in CI for Redis integration.
• Monitor pool exhausted metrics.

Common mistakes

• Default JDK serialization — opaque and fragile.
• New connection per request without pool.
• Missing timeout — threads hang on network partition.
• Mixing RedisTemplate serializers on same key prefix.

Advanced interview questions

Summary

Spring Data Redis + Lettuce = Boot default stack.