Cache Hit Ratio

Redis Cache Stats

# Get Redis stats
redis-cli INFO stats

# Key metrics:
# keyspace_hits: number of successful lookups
# keyspace_misses: number of failed lookups
# hit_ratio = hits / (hits + misses)

Magento Cache Metrics

use Magento\Framework\Cache\FrontendInterface;

class CacheMetrics
{
    private $cache;
    private $hits = 0;
    private $misses = 0;

    public function getHitRatio(): float
    {
        $total = $this->hits + $this->misses;
        if ($total === 0) return 0;
        return $this->hits / $total;
    }

    public function load($key)
    {
        $result = $this->cache->load($key);
        if ($result) {
            $this->hits++;
        } else {
            $this->misses++;
        }
        return $result;
    }
}

Monitor Cache Performance

# Redis monitoring
redis-cli MONITOR

# Check specific cache type
redis-cli GET "full_page_cache_*"

# Count cached items
redis-cli DBSIZE

Key Points

• Aim for 80%+ cache hit ratio
• Monitor hits and misses separately
• Track cache performance over time
• Identify cache-ineffective patterns

Increase Cache Lifetime

// Cache configuration
$cacheConfig = [
    'full_page_cache' => [
        'lifetime' => 86400,  // 24 hours
    ],
    'block_html' => [
        'lifetime' => 3600,   // 1 hour
    ],
    'config' => [
        'lifetime' => 86400,  // 24 hours
    ],
];

Reduce Cache Invalidation

// Avoid invalidating entire cache
// BAD: Cache::clean()
$this->cache->clean();

// GOOD: Invalidate specific tags
$this->cache->clean(
    'tags' => ['catalog_product_' . $productId]
);

Use Appropriate Cache Types

// Different cache for different data
$fullPageCache = $this->cacheManager->getCache('full_page');
$configCache = $this->cacheManager->getCache('config');
$blockCache = $this->cacheManager->getCache('block_html');

Key Points

• Longer lifetimes for stable data
• Tag-based invalidation for precision
• Separate caches by data type
• Avoid full cache clears

Pre-warm Cache

use Magento\Framework\App\Cache\TypeListInterface;

class CacheWarmer
{
    private $cacheTypeList;
    private $urlInterface;

    public function warmCache()
    {
        // Warm full page cache
        $urls = $this->getImportantUrls();
        foreach ($urls as $url) {
            $this->makeRequest($url);
        }
    }

    private function getImportantUrls(): array
    {
        return [
            $this->urlInterface->getBaseUrl(),
            '/catalogsearch/result/?q=test',
            '/customer/account/login',
        ];
    }
}

Cron-based Warming

<!-- cron.xml -->
<group id="default">
    <job name="cache_warmer" instance="Vendor\Module\Cron\CacheWarmer" method="execute">
        <schedule>*/5 * * * *</schedule>
    </job>
</group>

External Cache Warming

# Use wget/curl to warm cache
#!/bin/bash
URLS=(
    "https://magento.example.com/"
    "https://magento.example.com/category.html"
    "https://magento.example.com/product.html"
)

for url in "${URLS[@]}"; do
    curl -s -o /dev/null "$url"
done

Key Points

• Warm cache during low traffic
• Prioritize important pages
• Use cron for scheduled warming
• Monitor warming effectiveness

Cache Strategy Types

// 1. Cache-Aside (Lazy Loading)
$data = $cache->load($key);
if (!$data) {
    $data = $database->load($key);
    $cache->save(serialize($data), $key);
}

// 2. Write-Through
function save($key, $data) {
    $database->save($data);
    $cache->save(serialize($data), $key);
}

// 3. Write-Behind (Async)
function save($data) {
    $database->save($data);
    $queue->push($data);  // Async cache update
}

Magento Cache Layers

// Layer 1: Full Page Cache (Varnish/Redis)
// Layer 2: Block HTML Cache
// Layer 3: Config Cache
// Layer 4: Database Query Cache
// Layer 5: Object Cache

Key Points

• Use cache-aside for most scenarios
• Write-through for data consistency
• Multiple cache layers for performance
• Monitor each cache layer separately