Optimizing WordPress Performance on a VPS

Why WordPress is Slow (and How to Fix It)

WordPress out of the box serves every page dynamically — each request runs PHP, queries the database, and builds HTML. On a VPS, you control the entire stack and can dramatically improve performance.

Step 1: PHP Configuration

# /etc/php/8.3/fpm/php.ini
memory_limit = 256M
max_execution_time = 30
upload_max_filesize = 64M
post_max_size = 64M

# OPcache (crucial for PHP performance)
opcache.enable = 1
opcache.memory_consumption = 128
opcache.max_accelerated_files = 10000
opcache.validate_timestamps = 1
opcache.revalidate_freq = 60

Step 2: PHP-FPM Pool Tuning

# /etc/php/8.3/fpm/pool.d/www.conf
pm = dynamic
pm.max_children = 20
pm.start_servers = 5
pm.min_spare_servers = 3
pm.max_spare_servers = 10
pm.max_requests = 500

Step 3: Page Caching

Install a caching plugin that generates static HTML files:

Step 4: Object Caching with Redis

sudo apt install -y redis-server php8.3-redis

In wp-config.php:

define('WP_REDIS_HOST', '127.0.0.1');
define('WP_REDIS_PORT', 6379);

Install the "Redis Object Cache" plugin and enable it.

Step 5: Database Optimization

-- Clean up post revisions (keep last 5)
DELETE FROM wp_posts WHERE post_type = 'revision'
  AND ID NOT IN (
    SELECT * FROM (
      SELECT ID FROM wp_posts WHERE post_type = 'revision'
      ORDER BY post_date DESC LIMIT 5
    ) AS t
  );

-- Clean transients
DELETE FROM wp_options WHERE option_name LIKE '%_transient_%';

-- Optimize tables
mysqlcheck -o wordpress -u root -p

Limit revisions in wp-config.php:

define('WP_POST_REVISIONS', 5);
define('AUTOSAVE_INTERVAL', 120);
define('EMPTY_TRASH_DAYS', 7);

Step 6: Image Optimization

• Use WebP format (50-80% smaller than JPEG)
• Lazy load images below the fold
• Serve responsive images with srcset
• Use a CDN for static assets

Benchmarking

# Test page load time
curl -o /dev/null -s -w "Time: %{time_total}s\n" https://example.com

# Load testing
ab -n 100 -c 10 https://example.com/

Tip The single biggest WordPress performance improvement is page caching. A cached page serves in 20ms instead of 200-500ms. Everything else is secondary.