Azure Cache for Redis¶

Use Azure Cache for Redis with Spring Boot to reduce database load, accelerate reads, and share session state across scaled-out App Service instances.

Prerequisites¶

• Azure Cache for Redis instance available
• App Service app deployed and running
• Redis hostname, port (6380), and access key or Entra-based auth plan

Main Content¶

Architecture¶

flowchart TD
    C[Client] --> A[App Service Spring Boot]
    A --> R[Azure Cache for Redis TLS]
    A --> D[(Primary Database)]
    R -.cache hit.-> A
    D -.cache miss fallback.-> A

Maven dependencies (pom.xml)¶

<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.session</groupId>
    <artifactId>spring-session-data-redis</artifactId>
  </dependency>
</dependencies>

Spring Boot uses Lettuce as the default Redis client.

Redis TLS configuration (application.properties)¶

spring.data.redis.host=<redis-name>.redis.cache.windows.net
spring.data.redis.port=6380
spring.data.redis.password=${REDIS_ACCESS_KEY:}
spring.data.redis.ssl.enabled=true
spring.data.redis.timeout=2s

spring.session.store-type=redis
spring.session.redis.namespace=appservice-java-guide

App Settings for production¶

az webapp config appsettings set \
  --resource-group "$RG" \
  --name "$APP_NAME" \
  --settings \
    SPRING_DATA_REDIS_HOST="<redis-name>.redis.cache.windows.net" \
    SPRING_DATA_REDIS_PORT="6380" \
    SPRING_DATA_REDIS_SSL_ENABLED="true" \
    REDIS_ACCESS_KEY="<redacted>" \
  --output json

Cache-aside service pattern¶

@Service
public class ProductService {
    private final RedisTemplate<String, String> redisTemplate;

    public ProductService(RedisTemplate<String, String> redisTemplate) {
        this.redisTemplate = redisTemplate;
    }

    public String getCachedValue(String key, Supplier<String> loader) {
        String cached = redisTemplate.opsForValue().get(key);
        if (cached != null) {
            return cached;
        }
        String fresh = loader.get();
        redisTemplate.opsForValue().set(key, fresh, Duration.ofMinutes(10));
        return fresh;
    }
}

Session store pattern¶

With spring-session-data-redis, session state survives:

• instance restarts
• scale-out to multiple workers
• slot swaps (when routing moves)

Operational tuning guidance¶

• Keep value payloads compact
• Set explicit TTL on cache entries
• Use separate key prefixes by bounded context
• Monitor hit ratio and eviction trends

Verify connectivity endpoint pattern¶

@GetMapping("/api/redis/ping")
public Map<String, Object> redisPing(StringRedisTemplate redis) {
    String key = "ping:" + Instant.now().toString();
    redis.opsForValue().set(key, "ok", Duration.ofSeconds(30));
    return Map.of("status", redis.opsForValue().get(key));
}

Verification¶

• Deploy app with Redis dependencies/config
• Call /api/redis/ping and confirm response status
• Observe reduced latency on cache-hit paths
• Confirm sessions persist across restarts/scale-out

Troubleshooting¶

RedisConnectionFailureException¶

Validate host, key, TLS (ssl.enabled=true), and NSG/firewall network path.

Frequent cache misses¶

Review TTL policy and key design; ensure cache keys include stable identifiers.

Session reset after deployment¶

Check session namespace consistency and verify all instances point to the same Redis cache.

Run It in the Portal¶

Portal view: Identity blade (optional Microsoft Entra authentication path)¶

The Identity blade is relevant only if you extend this recipe from the default key-based REDIS_ACCESS_KEY configuration to the optional Microsoft Entra authentication path mentioned in the introduction. In the visible pre-enable state, System assigned is selected and Status is still Off; turning it On is the Portal step that creates the app identity before any Redis-side access mapping can happen. For the recipe's default flow, keep using the REDIS_ACCESS_KEY app setting and Spring Data Redis (Lettuce) configuration with spring.data.redis.ssl.enabled=true shown above.

See Also¶

• Managed Identity
• VNet Integration
• Tutorial: Scaling

Sources¶

• Quickstart: Use Azure Cache for Redis in Java
• Azure Cache for Redis documentation