Caching Strategies Explained

Caching Makes Apps Fast

But invalidation makes developers cry.

Cache-Aside (Lazy Loading)

Most common pattern:

function getUser($id) {
    $cached = Cache::get("user:{$id}");
    if ($cached) return $cached;

    $user = User::find($id);
    Cache::put("user:{$id}", $user, 3600);
    return $user;
}

Write-Through

Update cache when data changes:

function updateUser($id, $data) {
    $user = User::find($id);
    $user->update($data);
    Cache::put("user:{$id}", $user, 3600);
    return $user;
}

Cache Invalidation

The hard part:

// Time-based (TTL)
Cache::put('key', $value, 3600); // Expires in 1 hour

// Event-based
class User extends Model {
    protected static function booted() {
        static::saved(fn($user) => Cache::forget("user:{$user->id}"));
    }
}

// Tag-based
Cache::tags(['users'])->put("user:{$id}", $user);
Cache::tags(['users'])->flush(); // Clear all user caches

What to Cache

// Database queries (especially aggregates)
Cache::remember('stats:users', 3600, fn() => User::count());

// External API responses
Cache::remember("weather:{$city}", 1800, fn() => WeatherApi::get($city));

// Computed/rendered content
Cache::remember("post:{$id}:html", 86400, fn() => markdown($post->content));

Cache Stampede

When cache expires, many requests hit the database:

// Solution: Lock while regenerating
Cache::lock("user:{$id}:lock")->get(function () use ($id) {
    $user = User::find($id);
    Cache::put("user:{$id}", $user, 3600);
});

TTL Guidelines

• User sessions: 1-24 hours
• API responses: 5-60 minutes
• Computed stats: 1-24 hours
• Static content: 1+ days