life-echo/api/.agents/skills/redis-development/rules/data-hash-field-expiry.md

title, impact, impactDescription, tags, description, alwaysApply

title	impact	impactDescription	tags	description	alwaysApply
Use Hash Field Expiration for Per-Field TTL	MEDIUM	Fine-grained expiration without managing timers	hash, expiration, ttl, hexpire	Use Hash Field Expiration for Per-Field TTL	true

Use Hash Field Expiration for Per-Field TTL

Use hash field expiration (Redis 7.4+) to delete individual fields automatically from a hash after a specific period of time. This is useful for caching scenarios where different fields have different lifetimes, and is easier than managing expiration from your own code.

Correct: Use HEXPIRE to set per-field TTL on hash fields.

Python (redis-py):

import redis

client = redis.Redis(host='localhost', port=6379)

# Set hash fields
client.hset("sensor:sensor1", mapping={
    "air_quality": "256",
    "battery_level": "89"
})

# Set 60-second TTL on specific fields (Redis 7.4+)
client.hexpire("sensor:sensor1", 60, "air_quality", "battery_level")

Java (Jedis):

import redis.clients.jedis.UnifiedJedis;
import java.util.Map;
import java.util.HashMap;

try (UnifiedJedis jedis = new UnifiedJedis("redis://localhost:6379")) {
    Map<String, String> hashFields = new HashMap<>();
    hashFields.put("air_quality", "256");
    hashFields.put("battery_level", "89");

    jedis.hset("sensor:sensor1", hashFields);
    
    // Set 60-second TTL on specific fields (Redis 7.4+)
    jedis.hexpire("sensor:sensor1", 60, "air_quality", "battery_level");
}

When to use:

• Sensor data or metrics that become stale after a period
• Session attributes where different fields have different lifetimes
• Cached values within a hash that should auto-expire independently
• Temporary flags or tokens stored alongside persistent data

When NOT needed:

• Persistent user profiles or configuration
• Data where the entire hash should expire together (use EXPIRE on the key instead)
• Fields managed by application logic with explicit deletion

Reference: HEXPIRE command