Set Up Redis as Application Cache with TTL

Beginner10 minTrending

Configure Redis as a fast in-memory cache for your application with key expiration policies to manage memory efficiently.

Prerequisites

-Redis installed and running
-redis-cli available

Steps

Verify Redis is running

Confirm that your Redis server is up and responding to commands.

$ redis-cli ping

You should see PONG as the response. If not, start Redis with 'redis-server' or 'sudo systemctl start redis'.

Set a key with a TTL

Store a cached value with an automatic expiration time in seconds.

$ redis-cli SET user:1001:profile '{"name":"alice","email":"alice@example.com"}' EX 3600

EX sets expiration in seconds. Use PX for milliseconds.

Check remaining TTL on a key

Inspect how many seconds remain before a key expires.

$ redis-cli TTL user:1001:profile

Set a default eviction policy

Configure Redis to automatically evict least-recently-used keys when memory is full.

$ redis-cli CONFIG SET maxmemory-policy allkeys-lru

This changes the running config only. Add 'maxmemory-policy allkeys-lru' to redis.conf for persistence across restarts.

Set a memory limit

Cap Redis memory usage to prevent it from consuming all available RAM.

$ redis-cli CONFIG SET maxmemory 256mb

Verify cache hit and miss with GET

Retrieve a cached value and confirm it returns data before expiration and nil after.

$ redis-cli GET user:1001:profile

Full Script

full-script.sh

#!/bin/bash
# Redis Cache Setup
set -euo pipefail

echo "=== Verifying Redis ==="
redis-cli ping

echo ""
echo "=== Configuring memory and eviction ==="
redis-cli CONFIG SET maxmemory 256mb
redis-cli CONFIG SET maxmemory-policy allkeys-lru

echo ""
echo "=== Setting sample cached keys ==="
redis-cli SET user:1001:profile '{"name":"alice","email":"alice@example.com"}' EX 3600
redis-cli SET user:1002:profile '{"name":"bob","email":"bob@example.com"}' EX 3600
redis-cli SET api:rates:usd '{"rate":1.0}' EX 300

echo ""
echo "=== Verifying keys ==="
redis-cli TTL user:1001:profile
redis-cli GET user:1001:profile

echo ""
echo "=== Memory usage ==="
redis-cli INFO memory | grep used_memory_human

FAQ

Discussion

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#!/bin/bash # Redis Cache Setup set -euo pipefail echo "=== Verifying Redis ===" redis-cli ping echo "" echo "=== Configuring memory and eviction ===" redis-cli CONFIG SET maxmemory 256mb redis-cli CONFIG SET maxmemory-policy allkeys-lru echo "" echo "=== Setting sample cached keys ===" redis-cli SET user:1001:profile '{"name":"alice","email":"alice@example.com"}' EX 3600 redis-cli SET user:1002:profile '{"name":"bob","email":"bob@example.com"}' EX 3600 redis-cli SET api:rates:usd '{"rate":1.0}' EX 300 echo "" echo "=== Verifying keys ===" redis-cli TTL user:1001:profile redis-cli GET user:1001:profile echo "" echo "=== Memory usage ===" redis-cli INFO memory | grep used_memory_human