Implementing Cache Keys and TTL Policies

Well-designed cache keys include a namespace, schema version and every dimension affecting a result.

What It Does and When to Use It

Use namespace, schema version and locale so different representations do not collide. APCu stores local application data, Redis is external and can be shared among hosts, and OPcache stores compiled code.

Requirements, Inputs and Expected Behavior

Confirm the runtime, extension, environment variables, and permissions before running the examples in production. TTL does not replace explicit invalidation after a write and private data must be tenant scoped.

Example 1: Basic Operation

Use namespace, schema version and locale so different representations do not collide.

<?php
function cacheKey(int $productId,string $locale): string {
  return 'product:v2:'.$locale.':'.$productId;
}
echo cacheKey(45,'en');

Example 2: Behavior and Validation

Define explicit expiry and calculate remaining lifetime safely.

<?php
$now=time(); $expiresAt=$now+300;
echo 'Remaining TTL: ',max(0,$expiresAt-time()),' seconds';

Practical Example: Application Use

Add bounded TTL jitter to avoid synchronizing expiration for many hot entries.

<?php
$key='catalog:v4:page:1';
$ttl=random_int(270,330);
echo $key,' expires in ', $ttl,' seconds';

Important Behavior and Edge Cases

The second example highlights: Define explicit expiry and calculate remaining lifetime safely. The practical example adds: Add bounded TTL jitter to avoid synchronizing expiration for many hot entries.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Well-designed cache keys include a namespace, schema version and every dimension affecting a result.
• Add bounded TTL jitter to avoid synchronizing expiration for many hot entries.
• Define TTL, invalidation, and concurrency behavior separately from the cache storage API.