Auto‑Close Unpaid Orders with Redis Key Expiration Events in Spring Boot

Business Scenario

We use an order function as an example: after an order is created, if it is not paid within a certain time it should be automatically closed. Using a scheduled task is inefficient because order creation times differ, so we propose listening to Redis key expiration events to close orders automatically.

Implementation Idea

When creating an order, store a KV pair in Redis where the key is the order number (so we can locate the order in the database) and the value can be anything. Set the key's TTL to 30 minutes. When the key expires, Redis sends a notification, allowing us to close the unpaid order.

We listen to Redis's expiration event queue; when a key expires, Redis publishes a message containing the key ( K) but not the value ( V). Using the key we locate the order and, if it is still unpaid, update its status to closed or cancelled.

Enable Redis Key Expiration Notifications

Modify redis.conf to set notify-keyspace-events to include the appropriate flags. Add Ex to enable key‑event expiration notifications. The flags meaning: K – keyspace events, E – keyevent events, g – generic commands, $ – string commands, l – list commands, s – set commands, h – hash commands, z – sorted‑set commands, x – expired events, e – evicted events, A – all events.

Add Dependency

Add the Spring Boot starter for Redis in pom.xml:

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

Configuration

Create a RedisListenerConfig class to define a RedisMessageListenerContainer bean:

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;

@Configuration
public class RedisListenerConfig {
    @Bean
    RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        return container;
    }
}

Implement a listener extending KeyExpirationEventMessageListener to handle expired keys:

import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.listener.KeyExpirationEventMessageListener;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.stereotype.Component;

@Component
public class RedisKeyExpirationListener extends KeyExpirationEventMessageListener {
    public RedisKeyExpirationListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    @Override
    public void onMessage(Message message, byte[] pattern) {
        // Get the expired key and process order cancellation
        String expiredKey = message.toString();
        System.out.println(expiredKey);
    }
}