Cache Warming Strategies

Why Cache Warming

After deployment or cache flush, the first requests to each page are slow because caches are cold. Cache warming pre-populates caches before users visit.

Without warming:
  Request 1: 5000ms (cold)
  Request 2: 2000ms
  Request 3: 500ms (warm)

With warming:
  Preload: 30000ms (background)
  Request 1: 500ms (warm)
  Request 2: 500ms (warm)

Magento Cache Types

# List all cache types
bin/magento cache:status

# Enable all caches
bin/magento cache:enable

# Clean cache (invalidates entries)
bin/magento cache:clean

# Flush cache (removes all entries)
bin/magento cache:flush

Page Cache Warming Script

#!/bin/bash
# warm-cache.sh

BASE_URL="https://www.example.com"
PRODUCT_IDS=(1 2 3 4 5 10 15 20 25 30)
CATEGORY_IDS=(3 5 7 10 15)

echo "Warming page cache..."

# Homepage
echo "Warming homepage..."
curl -s -o /dev/null "$BASE_URL/"

# Category pages
echo "Warming category pages..."
for id in "${CATEGORY_IDS[@]}"; do
    curl -s -o /dev/null "$BASE_URL/catalog/category/view/id/$id"
done

# Product pages
echo "Warming product pages..."
for id in "${PRODUCT_IDS[@]}"; do
    curl -s -o /dev/null "$BASE_URL/catalog/product/view/id/$id"
done

# CMS pages
echo "Warming CMS pages..."
curl -s -o /dev/null "$BASE_URL/about-us"
curl -s -o /dev/null "$BASE_URL/contact"

echo "Cache warming complete!"

Key Takeaway

Cache warming pre-populates caches after deployment or flush. Use scripts to preload popular pages like homepage, categories, and products.

Post-Deployment Warming

# GitHub Actions post-deploy
warming:
  needs: deploy-production
  runs-on: ubuntu-latest
  steps:
    - name: Wait for Deployment
      run: sleep 30
    
    - name: Warm Cache
      run: |
        # Homepage
curl -s -o /dev/null https://www.example.com/
        
        # Top categories
        for id in 3 5 7 10; do
          curl -s -o /dev/null "https://www.example.com/catalog/category/view/id/$id"
        done
        
        # Top products
        for id in 1 2 3 4 5; do
          curl -s -o /dev/null "https://www.example.com/catalog/product/view/id/$id"
        done

Cron-Based Warming

<!-- app/code/Vendor/CacheWarmup/etc/crontab.xml -->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/crontab.xsd">
    <group id="default">
        <job name="cache_warmup" instance="Vendor\CacheWarmup\Cron\Warmup" method="execute">
            <schedule>*/5 * * * *</schedule>
        </job>
    </group>
</config>

<?php
namespace Vendor\CacheWarmup\Cron;

class Warmup
{
    private $httpClient;
    private $urlProvider;
    
    public function execute()
    {
        $urls = $this->urlProvider->getUrlsToWarm();
        
        foreach ($urls as $url) {
            $this->httpClient->request('GET', $url);
        }
    }
}

Cache Warming Service

<?php
namespace Vendor\CacheWarmup\Service;

class CacheWarmer
{
    private $productRepository;
    private $categoryFactory;
    private $pageRepository;
    
    public function warmAll(): void
    {
        $this->warmHomepage();
        $this->warmCategories();
        $this->warmProducts();
        $this->warmCmsPages();
    }
    
    private function warmHomepage(): void
    {
        $this->httpClient->request('GET', $this->storeManager->getStore()->getBaseUrl());
    }
    
    private function warmCategories(): void
    {
        $categories = $this->categoryFactory->create()
            ->addFieldToSelect('url_key')
            ->addFieldToFilter('is_active', 1)
            ->load();
            
        foreach ($categories as $category) {
            $this->httpClient->request('GET', $category->getUrl());
        }
    }
    
    private function warmProducts(): void
    {
        $products = $this->productRepository->getList(
            $this->searchCriteria->create()
        )->getItems();
        
        foreach ($products as $product) {
            $this->httpClient->request('GET', $product->getUrl());
        }
    }
}

Key Takeaway

Automate cache warming with post-deployment scripts, cron jobs, or services. Warm homepage, categories, products, and CMS pages.

Cache Hit Ratio Monitoring

# Check FPC hit ratio
bin/magento cache:status | grep page_cache

# Varnish hit ratio
varnishstat -f MAIN.cache_hit
varnishstat -f MAIN.cache_miss

# Redis hit ratio
redis-cli info stats | grep keyspace_hits
redis-cli info stats | grep keyspace_misses

Improving Hit Ratio

# Enable full page cache
bin/magento config:set system/full_page_cache/caching_application 2

# Configure TTL for different pages
bin/magento config:set dev/caching/ttl_configuration/catalog_category 86400
bin/magento config:set dev/caching/ttl_configuration/catalog_product 86400

Cache Tag Optimization

// Use specific cache tags instead of broad ones
$cache->save($data, $key, ['catalog_product_123']);

// Avoid clearing entire cache
$cache->clean(); // Bad - clears everything
$cache->remove('key', ['tag']); // Good - removes specific entry

Varnish Configuration

# Increase TTL for static content
sub vcl_backend_response {
    if (beresp.url ~ "\.(css|js|jpg|png)$") {
        set beresp.ttl = 7d;
    }
    if (beresp.http.Content-Type ~ "text/html") {
        set beresp.ttl = 15m;
    }
}

# Enable grace for stale content
sub vcl_backend_response {
    set beresp.grace = 24h;
}

Key Takeaway

Monitor cache hit ratios with Varnish and Redis stats. Improve with proper TTL settings, specific cache tags, and grace periods for stale content.