wp-performance-review

name wp-performance-review description WordPress performance code review and optimization analysis. Use when reviewing WordPress PHP code for performance issues, auditing themes/plugins for scalability, optimizing WP_Query, analyzing caching strategies, checking code before launch, or detecting anti-patterns, or when user mentions "performance review", "optimization audit", "slow WordPress", "slow queries", "high-traffic", "scale WordPress", "code review", "timeout", "500 error", "out of memory", or "site won't load". Detects anti-patterns in database queries, hooks, object caching, AJAX, and template loading. WordPress Performance Review Skill Overview Systematic performance code review for WordPress themes, plugins, and custom code. Core principle: Scan critical issues first (OOM, unbounded queries, cache bypass), then warnings, then optimizations. Report with line numbers and severity levels. When to Use Use when: Reviewing PR/code for WordPress theme or plugin User reports slow page loads, timeouts, or 500 errors Auditing before high-traffic event (launch, sale, viral moment) Optimizing WP_Query or database operations Investigating memory exhaustion or DB locks Don't use for: Security-only audits (use wp-security-review when available) Gutenberg block development patterns (use wp-gutenberg-blocks when available) General PHP code review not specific to WordPress Code Review Workflow Identify file type and apply relevant checks below Scan for critical patterns first (OOM, unbounded queries, cache bypass) Check warnings (inefficient but not catastrophic) Note optimizations (nice-to-have improvements) Report with line numbers using output format below File-Type Specific Checks Plugin/Theme PHP Files ( functions.php , plugin.php , *.php ) Scan for: query_posts() → CRITICAL: Never use - breaks main query posts_per_page.*-1 or numberposts.*-1 → CRITICAL: Unbounded query session_start() → CRITICAL: Bypasses page cache add_action.*init.* or add_action.*wp_loaded → Check if expensive code runs every request update_option or add_option in non-admin context → WARNING: DB writes on page load wp_remote_get or wp_remote_post without caching → WARNING: Blocking HTTP WP_Query / Database Code Scan for: Missing posts_per_page argument → WARNING: Defaults to blog setting 'meta_query' with 'value' comparisons → WARNING: Unindexed column scan post__not_in with large arrays → WARNING: Slow exclusion LIKE '%term%' (leading wildcard) → WARNING: Full table scan Missing no_found_rows => true when not paginating → INFO: Unnecessary count AJAX Handlers ( wp_ajax_* , REST endpoints) Scan for: admin-ajax.php usage → INFO: Consider REST API instead POST method for read operations → WARNING: Bypasses cache setInterval or polling patterns → CRITICAL: Self-DDoS risk Missing nonce verification → Security issue (not performance, but flag it) Template Files ( *.php in theme) Scan for: get_template_part in loops → WARNING: Consider caching output Database queries inside loops (N+1) → CRITICAL: Query multiplication wp_remote_get in templates → WARNING: Blocks rendering JavaScript Files Scan for: $.post( for read operations → WARNING: Use GET for cacheability setInterval.*fetch\|ajax → CRITICAL: Polling pattern import _ from 'lodash' → WARNING: Full library import bloats bundle Inline <script> making AJAX calls on load → Check necessity Block Editor / Gutenberg Files ( block.json , *.js in blocks/) Scan for: Many registerBlockStyle() calls → WARNING: Each creates preview iframe wp_kses_post($content) in render callbacks → WARNING: Breaks InnerBlocks Static blocks without render_callback → INFO: Consider dynamic for maintainability Asset Registration ( functions.php , *.php ) Scan for: wp_enqueue_script without version → INFO: Cache busting issues wp_enqueue_script without defer / async strategy → INFO: Blocks rendering Missing THEME_VERSION constant → INFO: Version management wp_enqueue_script without conditional check → WARNING: Assets load globally when only needed on specific pages Transients & Options Scan for: set_transient with dynamic keys (e.g., user_{$id} ) → WARNING: Table bloat without object cache set_transient for frequently-changing data → WARNING: Defeats caching purpose Large data in transients on shared hosting → WARNING: DB bloat without object cache WP-Cron Scan for: Missing DISABLE_WP_CRON constant → INFO: Cron runs on page requests Long-running cron callbacks (loops over all users/posts) → CRITICAL: Blocks cron queue wp_schedule_event without checking if already scheduled → WARNING: Duplicate schedules Search Patterns for Quick Detection # Critical issues - scan these first grep -rn "posts_per_page.*-1\|numberposts.*-1" . grep -rn "query_posts\s*(" . grep -rn "session_start\s*(" . grep -rn "setInterval.*fetch\|setInterval.*ajax\|setInterval.*\\\$\." . # Database writes on frontend grep -rn "update_option\|add_option" . | grep -v "admin\|activate\|install" # Uncached expensive functions grep -rn "url_to_postid\|attachment_url_to_postid\|count_user_posts" . # External HTTP without caching grep -rn "wp_remote_get\|wp_remote_post\|file_get_contents.*http" . # Cache bypass risks grep -rn "setcookie\|session_start" . # PHP code anti-patterns grep -rn "in_array\s*(" . | grep -v "true\s*)" # Missing strict comparison grep -rn "<<<" . # Heredoc/nowdoc syntax grep -rn "cache_results.*false" . # JavaScript bundle issues grep -rn "import.*from.*lodash['\"]" . # Full lodash import grep -rn "registerBlockStyle" . # Many block styles = performance issue # Asset loading issues grep -rn "wp_enqueue_script\|wp_enqueue_style" . | grep -v "is_page\|is_singular\|is_admin" # Transient misuse grep -rn "set_transient.*\\\$" . # Dynamic transient keys grep -rn "set_transient" . | grep -v "get_transient" # Set without checking first # WP-Cron issues grep -rn "wp_schedule_event" . | grep -v "wp_next_scheduled" # Missing schedule check Platform Context Different hosting environments require different approaches: Managed WordPress Hosts (WP Engine, Pantheon, Pressable, WordPress VIP, etc.): Often provide object caching out of the box May have platform-specific helper functions (e.g., wpcom_vip_* on VIP) Check host documentation for recommended patterns Self-Hosted / Standard Hosting : Implement object caching wrappers manually for expensive functions Consider Redis or Memcached plugins for persistent object cache More responsibility for caching layer configuration Shared Hosting : Be extra cautious about unbounded queries and external HTTP Limited resources mean performance issues surface faster May lack persistent object cache entirely Quick Reference: Critical Anti-Patterns Database Queries // ❌ CRITICAL: Unbounded query. 'posts_per_page' => - 1 // ✅ GOOD: Set reasonable limit, paginate if needed. 'posts_per_page' => 100 , 'no_found_rows' => true , // Skip count if not paginating. // ❌ CRITICAL: Never use query_posts(). query_posts ( 'cat=1' ); // Breaks pagination, conditionals. // ✅ GOOD: Use WP_Query or pre_get_posts filter. $query = new WP_Query ( array ( 'cat' => 1 ) ); // Or modify main query: add_action ( 'pre_get_posts' , function( $query ) { if ( $query -> is_main_query () && ! is_admin () ) { $query -> set ( 'cat' , 1 ); } } ); // ❌ CRITICAL: Missing WHERE clause (falsy ID becomes 0). $query = new WP_Query ( array ( 'p' => intval ( $maybe_false_id ) ) ); // ✅ GOOD: Validate ID before querying. if ( ! empty ( $maybe_false_id ) ) { $query = new WP_Query ( array ( 'p' => intval ( $maybe_false_id ) ) ); } // ❌ WARNING: LIKE with leading wildcard (full table scan). $wpdb -> get_results ( "SELECT * FROM wp_posts WHERE post_title LIKE '%term%'" ); // ✅ GOOD: Use trailing wildcard only, or use WP_Query 's' parameter. $wpdb -> get_results ( $wpdb -> prepare ( "SELECT * FROM wp_posts WHERE post_title LIKE %s" , $wpdb -> esc_like ( $term ) . '%' ) ); // ❌ WARNING: NOT IN queries (filter in PHP instead). 'post__not_in' => $excluded_ids // ✅ GOOD: Fetch all, filter in PHP (faster for large exclusion lists). $posts = get_posts ( array ( 'posts_per_page' => 100 ) ); $posts = array_filter ( $posts , function( $post ) use ( $ excluded_ids ) { return ! in_array ( $ post -> ID , $ excluded_ids , true ); } ); Hooks & Actions // ❌ WARNING: Code runs on every request via init. add_action ( 'init' , 'expensive_function' ); // ✅ GOOD: Check context before running expensive code. add_action ( 'init' , function() { if ( is_admin () || wp_doing_cron () ) { return ; } // Frontend-only code here. } ); // ❌ CRITICAL: Database writes on every page load. add_action ( 'wp_head' , 'prefix_bad_tracking' ); function prefix_bad_tracking ( ) { update_option ( 'last_visit' , time () ); } // ✅ GOOD: Use object cache buffer, flush via cron. add_action ( 'shutdown' , function() { wp_cache_incr ( 'page_views_buffer' , 1 , 'counters' ); } ); // ❌ WARNING: Using admin-ajax.php instead of REST API. // Prefer: register_rest_route() - leaner bootstrap. PHP Code // ❌ WARNING: O(n) lookup - use isset() with associative array. in_array ( $value , $array ); // Also missing strict = true. // ✅ GOOD: O(1) lookup with isset(). $allowed = array ( 'foo' => true , 'bar' => true ); if ( isset ( $allowed [ $value ] ) ) { // Process. } // ❌ WARNING: Heredoc prevents late escaping. $html = <<<HTML <div> $unescaped_content </div> HTML ; // ✅ GOOD: Escape at output. printf ( '<div>%s</div>' , esc_html ( $content ) ); Caching Issues // ❌ WARNING: Uncached expensive function calls. url_to_postid ( $url ); attachment_url_to_postid ( $attachment_url ); count_user_posts ( $user_id ); wp_oembed_get ( $url ); // ✅ GOOD: Wrap with object cache (works on any host). function prefix_cached_url_to_postid ( $url ) { $cache_key = 'url_to_postid_' . md5 ( $url ); $post_id = wp_cache_get ( $cache_key , 'url_lookups' ); if ( false === $post_id ) { $post_id = url_to_postid ( $url ); wp_cache_set ( $cache_key , $post_id , 'url_lookups' , HOUR_IN_SECONDS ); } return $post_id ; } // ✅ GOOD: On WordPress VIP, use platform helpers instead. // wpcom_vip_url_to_postid(), wpcom_vip_attachment_url_to_postid(), etc. // ❌ WARNING: Large autoloaded options. add_option ( 'prefix_large_data' , $data ); // Add: , '', 'no' for autoload. // ❌ INFO: Missing wp_cache_get_multiple for batch lookups. foreach ( $ids as $id ) { wp_cache_get ( "key_ {$id} " ); } AJAX & External Requests // ❌ WARNING: AJAX POST request (bypasses cache). $. post ( ajaxurl, data ); // Prefer: $.get() for read operations. // ❌ CRITICAL: Polling pattern (self-DDoS). setInterval ( () => fetch ( '/wp-json/...' ), 5000 ); // ❌ WARNING: Synchronous external HTTP in page load. wp_remote_get ( $url ); // Cache result or move to cron. // ✅ GOOD: Set timeout and handle errors. $response = wp_remote_get ( $url , array ( 'timeout' => 2 ) ); if ( is_wp_error ( $response ) ) { return get_fallback_data (); } WP Cron // ❌ WARNING: WP Cron runs on page requests. // Add to wp-config.php: define ( 'DISABLE_WP_CRON' , true ); // Run via server cron: * * * * * wp cron event run --due-now // ❌ CRITICAL: Long-running cron blocks entire queue. add_action ( 'my_daily_sync' , function() { foreach ( get_users () as $user ) { // 50k users = hours. sync_user_data ( $user ); } } ); // ✅ GOOD: Batch processing with rescheduling. add_action ( 'my_batch_sync' , function() { $offset = ( int ) get_option ( 'sync_offset' , 0 ); $users = get_users ( array ( 'number' => 100 , 'offset' => $offset ) );