wp-plugin-performance

name	wp-plugin-performance
description	Performance guidelines for WordPress plugin development: database optimization, object caching, conditional asset loading, efficient hooks, HTTP requests, WP-Cron, AJAX/REST optimization, and common anti-patterns. Based on official WordPress Developer Resources and WP VIP documentation.
compatibility	WordPress 6.0+ / PHP 7.4+. Applies to plugins and custom code.
license	GPL-2.0-or-later
metadata	{"author":"fernando-tellado","version":"1.0"}

WordPress plugin performance

When to use

Use this skill when:

• Developing new WordPress plugins
• Optimizing existing plugin code for better performance
• Working with database queries (WP_Query, $wpdb, options)
• Implementing caching strategies (object cache, transients)
• Loading assets (scripts, styles) efficiently
• Creating AJAX handlers or REST API endpoints
• Scheduling background tasks with WP-Cron
• Making external HTTP requests from plugins
• Reviewing code before deployment to high-traffic sites

Core performance principles

The performance mantra

Query only what you need
Cache expensive operations
Load assets conditionally
Avoid work on every request

Key concepts

1. Bounded queries: Always limit results with posts_per_page or similar
2. Object caching: Store expensive computations for reuse across requests
3. Conditional loading: Enqueue scripts/styles only where needed
4. Context awareness: Check is_admin(), page conditions before heavy operations
5. Async processing: Move slow tasks to WP-Cron or background processes

Database queries

Efficient database queries are the foundation of plugin performance.

WP_Query optimization

Parameter	Purpose
posts_per_page	Limit results (never use -1 in production)
no_found_rows	Skip counting total rows when not paginating
update_post_meta_cache	Set false if not using post meta
update_post_term_cache	Set false if not using taxonomies
fields	Request only 'ids' or 'id=>parent' when full objects not needed
cache_results	Keep true unless intentionally bypassing cache

WP_Query examples

// CORRECT: Optimized query for displaying 10 posts
$query = new WP_Query( array(
    'post_type'              => 'post',
    'posts_per_page'         => 10,
    'no_found_rows'          => true, // Skip SQL_CALC_FOUND_ROWS if not paginating
    'update_post_meta_cache' => false, // Skip if not using meta
    'update_post_term_cache' => false, // Skip if not using terms
) );

// CORRECT: Get only post IDs for a lightweight lookup
$post_ids = get_posts( array(
    'post_type'      => 'product',
    'posts_per_page' => 100,
    'fields'         => 'ids',
    'no_found_rows'  => true,
) );

// WRONG: Unbounded query - will crash on large sites
$all_posts = get_posts( array(
    'post_type'      => 'post',
    'posts_per_page' => -1, // Never do this in production!
) );

When pagination is needed

// CORRECT: With pagination - need found_rows for page links
$paged = get_query_var( 'paged' ) ? get_query_var( 'paged' ) : 1;

$query = new WP_Query( array(
    'post_type'      => 'post',
    'posts_per_page' => 10,
    'paged'          => $paged,
    // no_found_rows defaults to false - we need the count
) );

// Display pagination
echo paginate_links( array(
    'total' => $query->max_num_pages,
) );

Avoid query_posts()

// WRONG: Never use query_posts() - breaks main query and pagination
query_posts( 'cat=5' );

// CORRECT: Use pre_get_posts filter to modify main query
add_action( 'pre_get_posts', 'ayudawp_modify_main_query' );
function ayudawp_modify_main_query( $query ) {
    if ( ! is_admin() && $query->is_main_query() && $query->is_home() ) {
        $query->set( 'cat', 5 );
    }
}

// CORRECT: Use WP_Query for secondary queries
$custom_query = new WP_Query( array( 'cat' => 5 ) );

Meta queries optimization

Meta queries scan unindexed columns. Use them sparingly.

// WRONG: Complex meta query on every page load
$query = new WP_Query( array(
    'meta_query' => array(
        'relation' => 'AND',
        array(
            'key'     => 'color',
            'value'   => 'red',
            'compare' => '=',
        ),
        array(
            'key'     => 'size',
            'value'   => array( 'S', 'M', 'L' ),
            'compare' => 'IN',
        ),
    ),
) );

// CORRECT: Use taxonomy for filterable attributes
register_taxonomy( 'product_color', 'product', array( /* ... */ ) );
register_taxonomy( 'product_size', 'product', array( /* ... */ ) );

$query = new WP_Query( array(
    'tax_query' => array(
        'relation' => 'AND',
        array(
            'taxonomy' => 'product_color',
            'field'    => 'slug',
                => ,
        ),
        (
             => ,
                => ,
                => ( , ,  ),
        ),
    ),
) );

Post exclusion patterns

// WRONG: Large post__not_in arrays are slow
$query = new WP_Query( array(
    'post__not_in' => $hundreds_of_ids, // Slow!
) );

// CORRECT: Fetch all, filter in PHP (faster for large exclusions)
$posts = get_posts( array(
    'posts_per_page' => 100,
    'fields'         => 'ids',
) );

$filtered = array_diff( $posts, $excluded_ids );

Direct database queries

// CORRECT: Use $wpdb->prepare() with proper placeholders
global $wpdb;

$results = $wpdb->get_results(
    $wpdb->prepare(
        "SELECT ID, post_title FROM {$wpdb->posts} 
         WHERE post_type = %s AND post_status = %s 
         LIMIT %d",
        'product',
        'publish',
        100
    )
);

// WRONG: LIKE with leading wildcard - full table scan
$wpdb->get_results(
    $wpdb->prepare(
        "SELECT * FROM {$wpdb->posts} WHERE post_title LIKE %s",
        '%' . $wpdb->esc_like( $search ) . '%' // Leading % = slow
    )
);

// CORRECT: Trailing wildcard only when possible
$wpdb->get_results(
    $wpdb->prepare(
        "SELECT * FROM {$wpdb->posts} WHERE post_title LIKE %s",
        $wpdb->esc_like( $search ) . '%' // Trailing % = can use index
    )
);

Validate before querying

// WRONG: Query with potentially falsy ID
$post_id = get_some_id(); // Might return false, null, or 0
$query = new WP_Query( array( 'p' => intval( $post_id ) ) ); // p=0 returns posts!

// CORRECT: Validate before querying
$post_id = get_some_id();
if ( ! empty( $post_id ) && is_numeric( $post_id ) ) {
    $query = new WP_Query( array( 'p' => absint( $post_id ) ) );
}

Options and autoload

WordPress loads all autoloaded options on every page request.

Autoload guidelines

Data type	Autoload	Reason
Plugin settings (small)	Yes	Needed on most requests
Feature flags	Yes	Checked frequently
Large serialized data	No	Bloats memory on every request
Rarely used data	No	Only load when needed
Cached API responses	No	Use transients instead

Managing autoload

// CORRECT: Small settings - autoload is fine (default)
add_option( 'ayudawp_settings', array(
    'enabled' => true,
    'limit'   => 10,
) );

// CORRECT: Large data - disable autoload
add_option( 'ayudawp_large_data', $large_array, '', 'no' );

// CORRECT: Update existing option's autoload status
global $wpdb;
$wpdb->update(
    $wpdb->options,
    array( 'autoload' => 'no' ),
    array( 'option_name' => 'ayudawp_large_data' )
);

// Check total autoloaded size (for debugging)
$autoload_size = $wpdb->get_var(
    "SELECT SUM(LENGTH(option_value)) FROM {$wpdb->options} WHERE autoload = 'yes'"
);
// Target: under 800KB total

Avoid frequent option writes

// WRONG: Writing options on every page view
add_action( 'wp_head', 'ayudawp_bad_tracking' );
function ayudawp_bad_tracking() {
    $count = get_option( 'page_views', 0 );
    update_option( 'page_views', $count + 1 ); // DB write every request!
}

// CORRECT: Buffer in object cache, flush periodically
add_action( 'shutdown', 'ayudawp_buffer_tracking' );
function ayudawp_buffer_tracking() {
    wp_cache_incr( 'page_views_buffer', 1, 'ayudawp_stats' );
}

// Flush buffer via cron (hourly)
add_action( 'ayudawp_flush_stats', 'ayudawp_flush_view_buffer' );
function ayudawp_flush_view_buffer() {
    $buffered = wp_cache_get( 'page_views_buffer', 'ayudawp_stats' );
    if ( $buffered ) {
        $current = get_option( 'page_views', 0 );
        update_option( ,  +  );
        ( ,  );
    }
}

Object cache

Object cache stores data in memory for the duration of a request (or persistently with Redis/Memcached).

Object cache functions

Function	Purpose
wp_cache_get()	Retrieve cached value
wp_cache_set()	Store value in cache
wp_cache_add()	Store only if key doesn't exist
wp_cache_delete()	Remove cached value
wp_cache_incr()	Increment numeric value
wp_cache_get_multiple()	Batch retrieve (WP 5.5+)
wp_using_ext_object_cache()	Check if persistent cache available

Caching expensive operations

// CORRECT: Cache expensive function results
function ayudawp_get_complex_data( $user_id ) {
    $cache_key = 'complex_data_' . $user_id;
    $cache_group = 'ayudawp_data';
    
    $data = wp_cache_get( $cache_key, $cache_group );
    
    if ( false === $data ) {
        // Expensive operation
        $data = ayudawp_calculate_complex_data( $user_id );
        
        // Cache for 1 hour
        wp_cache_set( $cache_key, $data, $cache_group, HOUR_IN_SECONDS );
    }
    
    return $data;
}

// CORRECT: Invalidate cache when data changes
add_action( 'profile_update', 'ayudawp_clear_user_cache' );
function ayudawp_clear_user_cache( $user_id ) {
    wp_cache_delete( 'complex_data_' . $user_id, 'ayudawp_data' );
}

Expensive functions to cache

These WordPress functions are slow and should be cached:

// WRONG: Uncached expensive lookups
$post_id = url_to_postid( $url ); // Expensive!
$attachment_id = attachment_url_to_postid( $url ); // Very expensive!
$count = count_user_posts( $user_id ); // DB query each time
$oembed = wp_oembed_get( $url ); // External HTTP request

// CORRECT: Wrapper with cache
function ayudawp_cached_url_to_postid( $url ) {
    $cache_key = 'url_to_postid_' . md5( $url );
    $post_id = wp_cache_get( $cache_key, 'ayudawp_urls' );
    
    if ( false === $post_id ) {
        $post_id = url_to_postid( $url );
        wp_cache_set( $cache_key, $post_id, 'ayudawp_urls', DAY_IN_SECONDS );
    }
    
    return $post_id;
}

function ayudawp_cached_oembed( $url ) {
    $cache_key =  . (  );
     = ( ,  );
    
     (  ===  ) {
         = (  );
         (  ) {
            ( , , , DAY_IN_SECONDS );
        }
    }
    
     ;
}

Batch cache operations

// WRONG: Multiple cache calls in loop
foreach ( $user_ids as $user_id ) {
    $data = wp_cache_get( 'user_data_' . $user_id, 'ayudawp' ); // N calls
}

// CORRECT: Batch retrieve (WP 5.5+)
$cache_keys = array();
foreach ( $user_ids as $user_id ) {
    $cache_keys[] = 'user_data_' . $user_id;
}

$cached_data = wp_cache_get_multiple( $cache_keys, 'ayudawp' ); // 1 call

Transients

Transients provide expiring key-value storage. Without persistent object cache, they use the options table.

Transients vs object cache

Feature	Transients	Object cache
Expiration	Built-in	Optional
Persistence	Database (or object cache)	Memory (or persistent)
Use case	Data that expires	Request-level caching
Without Redis/Memcached	Uses wp_options	Non-persistent

Transient best practices

// CORRECT: API response caching
function ayudawp_get_external_data() {
    $transient_key = 'ayudawp_api_data';
    $data = get_transient( $transient_key );
    
    if ( false === $data ) {
        $response = wp_remote_get( 'https://api.example.com/data' );
        
        if ( ! is_wp_error( $response ) ) {
            $data = json_decode( wp_remote_retrieve_body( $response ), true );
            set_transient( $transient_key, $data, HOUR_IN_SECONDS );
        }
    }
    
    return $data;
}

// WRONG: Dynamic transient keys - causes table bloat without object cache
foreach ( $users as $user ) {
    set_transient( 'user_cache_' . $user->ID, $data, HOUR_IN_SECONDS );
    // 10,000 users = 10,000 rows in wp_options!
}

// CORRECT: Use object cache for user-specific data
foreach ( $users as $user ) {
    wp_cache_set( 'user_cache_' . ->ID, , , HOUR_IN_SECONDS );
}

Check object cache availability

// CORRECT: Adapt strategy based on environment
function ayudawp_cache_large_data( $key, $data, $expiration ) {
    if ( wp_using_ext_object_cache() ) {
        // Persistent object cache available - use transient (backed by object cache)
        set_transient( $key, $data, $expiration );
    } else {
        // No persistent cache - avoid bloating wp_options
        // Use filesystem cache or skip caching for this data
        ayudawp_file_cache_set( $key, $data, $expiration );
    }
}

Conditional asset loading

Load scripts and styles only where they are needed.

Enqueue patterns

// WRONG: Assets load on every page
add_action( 'wp_enqueue_scripts', 'ayudawp_bad_enqueue' );
function ayudawp_bad_enqueue() {
    wp_enqueue_script( 'ayudawp-gallery', AYUDAWP_URL . 'assets/js/gallery.js' );
    wp_enqueue_style( 'ayudawp-gallery', AYUDAWP_URL . 'assets/css/gallery.css' );
}

// CORRECT: Load only on pages with gallery shortcode
add_action( 'wp_enqueue_scripts', 'ayudawp_conditional_enqueue' );
function ayudawp_conditional_enqueue() {
    global $post;
    
    if ( is_singular() && has_shortcode( $post->post_content, 'ayudawp_gallery' ) ) {
        wp_enqueue_script( 'ayudawp-gallery', AYUDAWP_URL . 'assets/js/gallery.js', array(), AYUDAWP_VERSION, true );
        wp_enqueue_style( 'ayudawp-gallery', AYUDAWP_URL . 'assets/css/gallery.css', array(), AYUDAWP_VERSION );
    }
}

// CORRECT: Load on specific page templates
add_action( 'wp_enqueue_scripts', 'ayudawp_template_assets' );
function ayudawp_template_assets() {
     ( (  ) ) {
        ( , AYUDAWP_URL . , (), AYUDAWP_VERSION,  );
    }
}

Block-based conditional loading

// CORRECT: Enqueue only when block is present
function ayudawp_register_block_assets() {
    register_block_type( 'ayudawp/custom-block', array(
        'editor_script' => 'ayudawp-block-editor',
        'editor_style'  => 'ayudawp-block-editor-style',
        'script'        => 'ayudawp-block-frontend', // Only loads when block is used
        'style'         => 'ayudawp-block-style',     // Only loads when block is used
    ) );
}
add_action( 'init', 'ayudawp_register_block_assets' );

Dequeue unnecessary assets

// CORRECT: Remove assets not needed on specific pages
add_action( 'wp_enqueue_scripts', 'ayudawp_dequeue_unused', 100 );
function ayudawp_dequeue_unused() {
    // Remove block library CSS on pages without blocks
    if ( ! has_blocks() ) {
        wp_dequeue_style( 'wp-block-library' );
    }
    
    // Remove WooCommerce assets from non-shop pages
    if ( function_exists( 'is_woocommerce' ) ) {
        if ( ! is_woocommerce() && ! is_cart() && ! is_checkout() && ! is_account_page() ) {
            wp_dequeue_style( 'woocommerce-general' );
            wp_dequeue_style( 'woocommerce-layout' );
            wp_dequeue_script( 'wc-cart-fragments' );
        }
    }
}

Admin assets

// CORRECT: Load admin assets only on plugin pages
add_action( 'admin_enqueue_scripts', 'ayudawp_admin_assets' );
function ayudawp_admin_assets( $hook ) {
    // Only load on our settings page
    if ( 'settings_page_ayudawp-settings' !== $hook ) {
        return;
    }
    
    wp_enqueue_style( 'ayudawp-admin', AYUDAWP_URL . 'assets/css/admin.css', array(), AYUDAWP_VERSION );
    wp_enqueue_script( 'ayudawp-admin', AYUDAWP_URL . 'assets/js/admin.js', array( 'jquery' ), AYUDAWP_VERSION, true );
}

Efficient hooks

Avoid expensive operations in frequently-called hooks.

Hook execution frequency

Hook	Frequency	Suitable for
plugins_loaded	Every request	Class initialization, early setup
init	Every request	Register post types, taxonomies
wp_loaded	Every request	After all plugins loaded
wp	Frontend requests	Query-dependent setup
template_redirect	Frontend, before output	Redirects, access control
admin_init	Admin requests	Admin-only initialization
wp_head	Frontend, in head	Meta tags, early scripts
wp_footer	Frontend, in footer	Late scripts
shutdown	Every request, end	Cleanup, logging

Context-aware hooks

// WRONG: Expensive operation runs on every request
add_action( 'init', 'ayudawp_expensive_init' );
function ayudawp_expensive_init() {
    $data = ayudawp_fetch_remote_config(); // HTTP request on every page!
    // Process data...
}

// CORRECT: Check context before expensive operations
add_action( 'init', 'ayudawp_smart_init' );
function ayudawp_smart_init() {
    // Skip for AJAX, cron, REST API if not needed
    if ( wp_doing_ajax() || wp_doing_cron() || defined( 'REST_REQUEST' ) ) {
        return;
    }
    
    // Skip for admin if frontend-only feature
    if ( is_admin() ) {
        return;
    }
    
    // Now run the operation
    ayudawp_frontend_only_setup();
}

// CORRECT: Use appropriate hook for the task
add_action( 'template_redirect', 'ayudawp_check_access' );
function ayudawp_check_access() {
    // Runs only on frontend, after query is set up
    if ( is_singular( 'premium_content' ) && ! () ) {
        ( (  ) );
        ;
    }
}

Lazy loading patterns

// CORRECT: Initialize expensive objects only when needed
class AyudaWP_Heavy_Feature {
    private static $instance = null;
    
    public static function get_instance() {
        if ( null === self::$instance ) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    private function __construct() {
        // Expensive initialization here
    }
}

// Hook that triggers lazy loading
add_action( 'ayudawp_feature_needed', function() {
    AyudaWP_Heavy_Feature::get_instance()->run();
} );

Admin notices optimization

// WRONG: Check conditions on every admin page
add_action( 'admin_notices', 'ayudawp_check_requirements' );
function ayudawp_check_requirements() {
    $requirements = ayudawp_expensive_requirements_check(); // Runs on every admin page!
    if ( ! $requirements['met'] ) {
        echo '<div class="notice notice-error">...</div>';
    }
}

// CORRECT: Cache requirement checks
add_action( 'admin_notices', 'ayudawp_cached_requirements_notice' );
function ayudawp_cached_requirements_notice() {
    $cache_key = 'ayudawp_requirements_check';
    $requirements = get_transient( $cache_key );
    
    if ( false === $requirements ) {
        $requirements = ayudawp_expensive_requirements_check();
        set_transient( $cache_key, $requirements, HOUR_IN_SECONDS );
    }
    
    if ( ! $requirements['met'] ) {
        echo '<div class="notice notice-error">...</div>';
    }
}

// Clear cache when relevant options change
add_action( 'update_option_ayudawp_settings', function() {
    (  );
} );

External HTTP requests

HTTP requests to external APIs can significantly slow down page loads.

HTTP request best practices

// WRONG: No timeout, no error handling
$response = wp_remote_get( 'https://api.example.com/data' );
$body = wp_remote_retrieve_body( $response );

// CORRECT: Set timeout, handle errors, cache response
function ayudawp_fetch_api_data() {
    $cache_key = 'ayudawp_api_response';
    $cached = get_transient( $cache_key );
    
    if ( false !== $cached ) {
        return $cached;
    }
    
    $response = wp_remote_get( 'https://api.example.com/data', array(
        'timeout' => 5, // 5 seconds max
        'sslverify' => true,
    ) );
    
    if ( is_wp_error( $response ) ) {
        // Log error, return fallback
        error_log( 'AyudaWP API error: ' . $response->get_error_message() );
        return ayudawp_get_fallback_data();
    }
    
    $code = wp_remote_retrieve_response_code( $response );
    if ( 200 !==  ) {
        (  .  );
         ();
    }
    
     = (  );
     = ( ,  );
    
     ( () !== JSON_ERROR_NONE ) {
         ();
    }
    
    
    ( , , HOUR_IN_SECONDS );
    
     ;
}

Move HTTP requests to background

// WRONG: Sync API call blocks page load
add_action( 'save_post', 'ayudawp_notify_external_service' );
function ayudawp_notify_external_service( $post_id ) {
    wp_remote_post( 'https://api.example.com/notify', array(
        'body' => array( 'post_id' => $post_id ),
    ) ); // Blocks until complete!
}

// CORRECT: Schedule for background processing
add_action( 'save_post', 'ayudawp_schedule_notification' );
function ayudawp_schedule_notification( $post_id ) {
    if ( ! wp_next_scheduled( 'ayudawp_send_notification', array( $post_id ) ) ) {
        wp_schedule_single_event( time(), 'ayudawp_send_notification', array( $post_id ) );
    }
}

add_action( 'ayudawp_send_notification', 'ayudawp_do_notification' );
function ayudawp_do_notification( $post_id ) {
    wp_remote_post( 'https://api.example.com/notify', array(
            => (  =>  ),
         => , 
    ) );
}

WP-Cron

WP-Cron runs on page requests by default. Configure it properly for reliability.

WP-Cron configuration

// In wp-config.php: Disable WordPress cron trigger
define( 'DISABLE_WP_CRON', true );

// Set up real server cron instead:
// * * * * * cd /path/to/wordpress && wp cron event run --due-now > /dev/null 2>&1
// Or:
// * * * * * curl -s https://example.com/wp-cron.php?doing_wp_cron > /dev/null 2>&1

Scheduling events correctly

// WRONG: Schedule without checking if already scheduled
add_action( 'init', 'ayudawp_schedule_tasks' );
function ayudawp_schedule_tasks() {
    wp_schedule_event( time(), 'hourly', 'ayudawp_hourly_task' ); // Creates duplicates!
}

// CORRECT: Check before scheduling
add_action( 'init', 'ayudawp_schedule_tasks' );
function ayudawp_schedule_tasks() {
    if ( ! wp_next_scheduled( 'ayudawp_hourly_task' ) ) {
        wp_schedule_event( time(), 'hourly', 'ayudawp_hourly_task' );
    }
}

// CORRECT: Schedule on activation, clear on deactivation
register_activation_hook( __FILE__, 'ayudawp_activate' );
function ayudawp_activate() {
    if ( ! wp_next_scheduled( 'ayudawp_hourly_task' ) ) {
        wp_schedule_event( time(), 'hourly', 'ayudawp_hourly_task' );
    }
}

register_deactivation_hook( __FILE__, 'ayudawp_deactivate' );
{
    (  );
}

Batch processing for large datasets

// WRONG: Process all items in one cron run
add_action( 'ayudawp_sync_users', 'ayudawp_sync_all_users' );
function ayudawp_sync_all_users() {
    $users = get_users(); // 50,000 users = timeout!
    foreach ( $users as $user ) {
        ayudawp_sync_user( $user );
    }
}

// CORRECT: Process in batches with rescheduling
add_action( 'ayudawp_sync_users_batch', 'ayudawp_sync_users_batch' );
function ayudawp_sync_users_batch() {
    $batch_size = 100;
    $offset = (int) get_option( 'ayudawp_sync_offset', 0 );
    
    $users = get_users( array(
        'number' => $batch_size,
        'offset' => $offset,
    ) );
    
    // No more users - reset and stop
    if ( empty( $users ) ) {
        delete_option( 'ayudawp_sync_offset' );
        return;
    }
    
    // Process batch
    foreach (    ) {
        (  );
    }
    
    
    ( ,  +  );
    ( () + ,  );
}

Custom cron intervals

// Add custom interval
add_filter( 'cron_schedules', 'ayudawp_custom_cron_intervals' );
function ayudawp_custom_cron_intervals( $schedules ) {
    $schedules['fifteen_minutes'] = array(
        'interval' => 15 * MINUTE_IN_SECONDS,
        'display'  => __( 'Every 15 minutes', 'ayudawp' ),
    );
    return $schedules;
}

AJAX and REST API optimization

AJAX best practices

// WRONG: POST request for read-only operation
jQuery.post( ajaxurl, {
    action: 'ayudawp_get_data',
    nonce: ayudawp.nonce
}, function( response ) {
    // POST requests bypass page cache
});

// CORRECT: GET request for read operations (cacheable)
jQuery.get( ayudawp.rest_url + 'ayudawp/v1/data', {
    _wpnonce: ayudawp.nonce
}, function( response ) {
    // GET requests can be cached
});

Avoid polling patterns

// WRONG: Polling creates self-DDoS
setInterval( function() {
    fetch( '/wp-json/ayudawp/v1/updates' );
}, 5000 ); // 12 requests/minute per user!

// CORRECT: Use WebSockets, Server-Sent Events, or long-polling with backoff
let pollInterval = 5000;
const maxInterval = 60000;

function pollUpdates() {
    fetch( '/wp-json/ayudawp/v1/updates' )
        .then( response => response.json() )
        .then( data => {
            if ( data.hasUpdates ) {
                // Process updates, reset interval
                pollInterval = 5000;
            } else {
                // Exponential backoff
                pollInterval = Math.min( pollInterval * 1.5, maxInterval );
            }
            setTimeout( pollUpdates, pollInterval );
        } );
}

REST API optimization

// CORRECT: Optimized REST endpoint
register_rest_route( 'ayudawp/v1', '/items', array(
    'methods'             => 'GET',
    'callback'            => 'ayudawp_get_items',
    'permission_callback' => '__return_true', // Public endpoint
    'args'                => array(
        'per_page' => array(
            'default'           => 10,
            'sanitize_callback' => 'absint',
            'validate_callback' => function( $value ) {
                return $value > 0 && $value <= 100;
            },
        ),
    ),
) );

function ayudawp_get_items( $request ) {
    $per_page = $request->get_param( 'per_page' );
    
    // Use object cache
    $cache_key = 'items_' . $per_page;
    $items = wp_cache_get( $cache_key, 'ayudawp_api' );
    
    if ( false === $items ) {
        $items = get_posts( (
                  => ,
             => ,
              => ,
                     => ,
        ) );
        
        ( , , ,  * MINUTE_IN_SECONDS );
    }
    
     (  );
}

Common anti-patterns

PHP anti-patterns

// WRONG: O(n) array search
if ( in_array( $value, $large_array ) ) { // Also missing strict mode
    // ...
}

// CORRECT: O(1) lookup with isset
$lookup = array_flip( $large_array );
if ( isset( $lookup[ $value ] ) ) {
    // ...
}

// Or with strict comparison
if ( in_array( $value, $large_array, true ) ) {
    // ...
}

// WRONG: Heredoc prevents late escaping
$html = <<<HTML
<div class="widget">
    <h3>{$title}</h3>
    <p>{$content}</p>
</div>
HTML;

// CORRECT: Escape at output
printf(
    '<div class="widget"><h3>%s</h3><p>%s</p></div>',
    esc_html( $title ),
    wp_kses_post( $content )
);

Cache bypass issues

// WRONG: Sessions bypass full page cache
session_start(); // Entire site becomes uncacheable!

// CORRECT: Use WordPress user meta or custom cookies handled at edge
update_user_meta( get_current_user_id(), 'preference', $value );

// WRONG: Setting cookies on public pages
setcookie( 'visitor_tracking', $id ); // Prevents caching for this user

// CORRECT: Use localStorage in JavaScript, or track server-side only for logged-in users

N+1 query problems

// WRONG: Query in template loop
while ( have_posts() ) {
    the_post();
    $author_data = get_userdata( get_the_author_meta( 'ID' ) ); // Query per post!
    $custom_field = get_post_meta( get_the_ID(), 'custom', true ); // Query per post!
}

// CORRECT: Prime caches before loop
$post_ids = wp_list_pluck( $posts, 'ID' );
$author_ids = wp_list_pluck( $posts, 'post_author' );

update_meta_cache( 'post', $post_ids ); // Single query for all meta
cache_users( $author_ids ); // Single query for all authors

while ( have_posts() ) {
    the_post();
    // Now these use cached data
    $author_data = get_userdata( get_the_author_meta( 'ID' ) );
    $custom_field = get_post_meta( get_the_ID(), 'custom', true );
}

Measurement and profiling

Query Monitor

Query Monitor is the essential tool for WordPress performance debugging.

Key panels to check:

• Queries: Identify slow queries, duplicates, queries by component
• Request: Time breakdown by component
• Transients: Transient usage and database hits
• HTTP API Calls: External requests and timing
• Hooks & Actions: Hook execution order and timing

Debug constants

// In wp-config.php for development
define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );
define( 'SAVEQUERIES', true ); // Logs all queries (disable in production!)
define( 'SCRIPT_DEBUG', true );

Custom timing

// Measure execution time
function ayudawp_measure_operation() {
    $start = microtime( true );
    
    // Operation to measure
    ayudawp_expensive_operation();
    
    $elapsed = microtime( true ) - $start;
    
    if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
        error_log( sprintf( 'AyudaWP operation took %.4f seconds', $elapsed ) );
    }
}

Server-Timing header

// Add Server-Timing header for browser DevTools
add_action( 'send_headers', 'ayudawp_add_server_timing' );
function ayudawp_add_server_timing() {
    global $timestart;
    
    $total = microtime( true ) - $timestart;
    
    header( sprintf( 'Server-Timing: total;dur=%.2f', $total * 1000 ) );
}

Code review checklist

Database queries

• All queries have bounded results (posts_per_page is set)
• No posts_per_page => -1 in production code
• no_found_rows => true used when not paginating
• Meta caches disabled if not using meta (update_post_meta_cache => false)
• Term caches disabled if not using terms (update_post_term_cache => false)
• No query_posts() usage
• Input validated before querying (no falsy IDs)
• Meta queries replaced with taxonomies where possible

Caching

• Expensive operations wrapped with object cache
• Transients used for expiring data, not user-specific data
• No dynamic transient keys without persistent object cache
• Cache invalidation implemented when data changes
• wp_cache_get_multiple() used for batch operations

Options

• Large data stored with autoload => no
• No frequent option writes on frontend
• Option updates batched where possible

Assets

• Scripts/styles enqueued conditionally
• Assets loaded only on pages where needed
• Admin assets limited to plugin pages
• Unused assets dequeued

Hooks

• No expensive operations in init, plugins_loaded
• Context checks before heavy operations (is_admin(), etc.)
• Lazy loading for expensive objects

HTTP requests

• All requests have timeout set
• Error handling for failed requests
• Responses cached when appropriate
• Sync requests moved to background when possible

WP-Cron

• wp_next_scheduled() checked before scheduling
• Events cleared on plugin deactivation
• Long-running tasks use batch processing
• DISABLE_WP_CRON recommended in documentation

AJAX/REST

• GET used for read operations
• No polling patterns (or proper backoff implemented)
• Responses cached where appropriate
• Endpoints have proper validation

General

• No session_start() usage
• No cookies set on public pages
• Strict comparison used (===, in_array(..., true))
• No N+1 query patterns in loops

References

• WordPress Performance Optimization
• WordPress Caching
• PHP Optimization
• Plugin Best Practices
• WP_Query Class Reference
• Transients API
• WP_Object_Cache
• WP-Cron
• WordPress VIP Performance Docs
• Query Monitor Plugin