Drupal Performance Issues | Blue Frog Docs

Drupal Performance Issues

Troubleshoot and resolve performance issues on Drupal websites.

Drupal Performance Issues

Platform-specific guides for diagnosing and fixing Core Web Vitals and performance issues on Drupal.

Core Web Vitals

Largest Contentful Paint (LCP)

Fix slow main content loading on Drupal. Target: under 2.5 seconds.

Cumulative Layout Shift (CLS)

Resolve visual stability issues causing layout shifts. Target: under 0.1.

Common Drupal Performance Issues

Database Performance

Drupal's database-driven architecture can create performance bottlenecks if not properly optimized.

Common issues:

  • Inefficient queries from contrib modules
  • Missing database indexes
  • Large database tables (watchdog, cache_* tables)
  • Excessive database connections
  • Unoptimized Views queries

Optimization strategies:

  • Enable query logging to identify slow queries
  • Add indexes to frequently queried fields
  • Regularly truncate watchdog and cache tables
  • Use Redis or Memcached for database query caching
  • Optimize Views with proper filters and caching
  • Use the Devel module's query log during development

Drupal configuration:

// settings.php
$settings['database_cache_max_rows'] = ['default' => 5000];

Caching Strategies

Drupal's multi-layered caching system is critical for performance.

Page caching:

  • Enable Drupal's internal page cache for anonymous users
  • Set appropriate cache lifetimes (600-3600 seconds recommended)
  • Use Smart Cache or Cache Tags for granular invalidation
  • Implement BigPipe for progressive page rendering (Drupal 8+)

Dynamic page cache (Drupal 8+):

// Enable for authenticated users
$config['system.performance']['cache']['page']['max_age'] = 3600;

Block caching:

  • Configure per-block cache settings
  • Use cache contexts and tags appropriately
  • Cache menu blocks separately from content blocks

Views caching:

  • Enable time-based or tag-based caching for Views
  • Cache Views results and rendered output separately
  • Use "Search API" for complex listing pages

External caching layers:

  • Implement Varnish for reverse proxy caching
  • Use Redis or Memcached for backend caching
  • Configure CloudFlare or Fastly for edge caching

Drupal cache configuration:

// settings.php - Redis configuration
$settings['redis.connection']['interface'] = 'PhpRedis';
$settings['redis.connection']['host'] = '127.0.0.1';
$settings['redis.connection']['port'] = 6379;
$settings['cache']['default'] = 'cache.backend.redis';

Theme and Template Optimization

Common problems:

  • Excessive Twig template processing
  • Unoptimized theme hooks and preprocess functions
  • Too many regions loading on every page
  • Heavy base themes (Bootstrap, Foundation)

Solutions:

  • Disable Twig debugging in production
  • Use Twig template caching
  • Minimize preprocessing logic
  • Remove unused theme regions
  • Use lightweight base themes or custom themes
  • Aggregate and minify CSS/JS files

Twig optimization:

// settings.php - Disable Twig debugging
$settings['twig_debug'] = FALSE;
$settings['twig_cache'] = TRUE;
$settings['twig_auto_reload'] = FALSE;

Module Performance

Contributed modules can significantly impact Drupal performance.

Performance-heavy modules to watch:

  • Views (especially with complex relationships)
  • Panels/Page Manager (excessive layout processing)
  • Token module (recursive token replacement)
  • Webform (complex form processing)
  • Search API (indexing overhead)

Best practices:

  • Audit enabled modules quarterly
  • Disable unused modules completely (don't just uninstall)
  • Use lightweight alternatives when possible
  • Monitor module query counts with Devel
  • Update modules regularly for performance patches
  • Use Drush commands for module management

Check module overhead:

drush php-eval "print_r(module_list());"

Image Optimization

Drupal-specific image handling:

  • Use Image Styles for automatic resizing and caching
  • Enable lazy loading module for below-fold images
  • Configure WebP image format with fallbacks
  • Use responsive image module for srcset generation
  • Set appropriate image quality in Image Style settings (80-85% recommended)

Image Style configuration:

// Example: Optimize image quality
$config['image.style.large']['effects']['image_scale']['data']['quality'] = 85;

Recommended modules:

  • ImageAPI Optimize - Automated image compression
  • Lazy Load - Defer offscreen images
  • Responsive Images - Automatic srcset generation
  • WebP - Modern image format support

JavaScript and CSS Aggregation

Drupal's asset management:

  • Enable CSS and JS aggregation in performance settings
  • Use Advanced CSS/JS Aggregation module for better optimization
  • Implement critical CSS for above-the-fold content
  • Defer non-critical JavaScript loading
  • Remove unused libraries from pages

Configuration:

// Enable aggregation
$config['system.performance']['css']['preprocess'] = TRUE;
$config['system.performance']['js']['preprocess'] = TRUE;

Advanced aggregation settings:

  • Enable GZIP compression
  • Combine multiple CSS/JS files
  • Minify aggregated assets
  • Implement async/defer attributes

Drupal-Specific Performance Modules

Essential Performance Modules

Drupal 7:

  • Boost - Static page caching for maximum performance
  • Varnish - Reverse proxy integration
  • Memcache API and Integration - Memory-based caching
  • Advanced CSS/JS Aggregation - Better asset optimization
  • ImageAPI Optimize - Automatic image compression

Drupal 8/9/10:

  • Advanced CSS/JS Aggregation - Enhanced asset bundling
  • Redis - High-performance caching backend
  • Varnish Purge - Automated cache invalidation
  • Lazy Load - Image lazy loading
  • Fast 404 - Optimize 404 error handling

Performance Monitoring Modules

  • Devel - Query and performance debugging
  • Webprofiler - Detailed performance profiling
  • New Relic APM - Application performance monitoring
  • Performance Profiler - Track page generation times

Platform-Specific Troubleshooting

Slow Admin Pages

Admin pages in Drupal often perform poorly due to heavy processing.

Causes:

  • Complex administrative Views
  • Module configuration forms with heavy processing
  • Node edit forms with many fields
  • Media library browsing

Fixes:

  • Use Admin Toolbar module for streamlined navigation
  • Optimize administrative Views with proper caching
  • Implement field groups to reduce field loading
  • Use Media Library optimizations for large media collections

Slow Content Listing Pages

Optimization strategies:

  • Use Views with appropriate caching settings
  • Implement pager limits (25-50 items recommended)
  • Add database indexes to sorted/filtered fields
  • Use Search API instead of Views for large datasets
  • Cache Views results and rendered output separately

Entity Query Performance

Best practices:

  • Use EntityQuery for better performance over direct database queries
  • Implement proper access checks to leverage caching
  • Add database indexes for frequently queried fields
  • Use Query Tags for query alteration hooks
  • Limit query results with range() method

Form Performance

Heavy forms can slow down Drupal significantly.

Optimization techniques:

  • Reduce number of fields loaded simultaneously
  • Use field groups with collapsible fieldsets
  • Implement AJAX for dependent fields instead of full reloads
  • Disable autocomplete for large datasets
  • Use Select2 or Chosen modules for better select performance

Drupal Hosting and Infrastructure

PHP optimization:

; php.ini recommendations
memory_limit = 256M
max_execution_time = 60
upload_max_filesize = 64M
post_max_size = 64M
opcache.enable = 1
opcache.memory_consumption = 256
opcache.max_accelerated_files = 10000

Database optimization (MySQL/MariaDB):

; my.cnf recommendations
innodb_buffer_pool_size = 2G
innodb_log_file_size = 512M
query_cache_size = 64M
query_cache_type = 1

Content Delivery Network (CDN)

CDN integration:

  • Use CDN module for automatic asset URL rewriting
  • Configure CloudFlare, Fastly, or Akamai
  • Serve static assets from CDN
  • Implement proper cache headers
  • Use CDN for file downloads and media

CDN module configuration:

// settings.php
$config['cdn.settings']['status'] = TRUE;
$config['cdn.settings']['cdn_domain'] = 'cdn.example.com';

Drupal-Specific Performance Testing

Drush commands for performance:

# Clear all caches
drush cr

# Rebuild cache
drush cache-rebuild

# Check system status
drush status

# Run cron for cache maintenance
drush cron

# Analyze Views performance
drush views-analyze

Performance profiling:

  • Use XHProf or Blackfire.io for PHP profiling
  • Enable Webprofiler for detailed performance data
  • Monitor with New Relic or AppDynamics
  • Use MySQL slow query log

Diagnostic Tools

  1. Google PageSpeed Insights - Core Web Vitals analysis
  2. Chrome DevTools Performance Tab - Detailed waterfall analysis
  3. Lighthouse - Comprehensive performance audit
  4. Drupal Devel Module - Query and performance debugging
  5. Webprofiler - Request profiling and optimization suggestions
  6. Drush - Command-line diagnostics and cache management

Key Metrics for Drupal

Performance targets:

Advanced Performance Techniques

Implement Varnish Caching

Varnish provides powerful reverse proxy caching for Drupal.

VCL configuration for Drupal:

# Remove cookies for static assets
if (req.url ~ "\.(jpg|jpeg|gif|png|ico|css|js|svg|woff)$") {
    unset req.http.cookie;
}

# Cache purging for Drupal
if (req.method == "PURGE") {
    return (purge);
}

Database Replication

For high-traffic sites, implement database replication:

  • Master database for writes
  • Slave databases for reads
  • Configure in settings.php
$databases['default']['slave'][] = [
  'database' => 'drupal',
  'username' => 'drupal_slave',
  'password' => 'password',
  'host' => 'slave-db-server',
  'driver' => 'mysql',
];

Implement BigPipe (Drupal 8+)

BigPipe allows progressive page rendering for faster perceived performance.

// Enable BigPipe module
drush en bigpipe -y

Optimize Cron Operations

Heavy cron tasks can impact site performance.

Best practices:

  • Run cron externally via Drush or cURL
  • Schedule resource-intensive operations during off-peak hours
  • Split heavy operations into smaller batches
  • Monitor cron execution time
# External cron via Drush
*/15 * * * * cd /path/to/drupal && drush cron

Ongoing Maintenance

Regular Performance Audits

Monthly tasks:

  1. Review slow query log
  2. Check database table sizes
  3. Audit enabled modules
  4. Test page load times across site sections
  5. Monitor Core Web Vitals in Google Search Console
  6. Review cache hit ratios

Update Strategy

  • Keep Drupal core updated for performance improvements
  • Update contributed modules regularly
  • Test updates in staging environment first
  • Monitor Drupal.org security advisories
  • Use Composer for dependency management (Drupal 8+)

General Fixes

For universal performance concepts, see the Global Performance Issues Hub.

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