Bits of .NET

WordPress admin panel sluggish and using 100% CPU? The Heartbeat API polls your server every 15 seconds for autosave and notifications, eating resources.

What Heartbeat Does:

Every 15 seconds:
- Check for new comments
- Check for plugin updates  
- Autosave post drafts
- Notify about other users editing same post
- Trigger scheduled tasks

Result: 240 requests per hour per admin user
On busy sites: Server struggles, admin panel freezes

The Fix – Disable Heartbeat:

Add to functions.php (or use plugin “Heartbeat Control”):

// Completely disable Heartbeat
add_action('init', function() {
    wp_deregister_script('heartbeat');
}, 1);

Better: Control It Instead of Disabling:

// Slow down Heartbeat to 60 seconds (instead of 15)
add_filter('heartbeat_settings', function($settings) {
    $settings['interval'] = 60; // seconds
    return $settings;
});

// Disable Heartbeat on frontend (keep for admin)
add_action('init', function() {
    if (!is_admin()) {
        wp_deregister_script('heartbeat');
    }
}, 1);

// Disable everywhere except post editor
add_action('init', function() {
    global $pagenow;
    if ($pagenow != 'post.php' && $pagenow != 'post-new.php') {
        wp_deregister_script('heartbeat');
    }
}, 1);

Performance Impact:

Before (15 sec interval):
- 240 requests/hour/user
- 10 active admins = 2400 requests/hour
- Each request: 50-200ms server time
- Total server load: 2-8 minutes CPU per hour

After (60 sec interval):
- 60 requests/hour/user  
- 10 active admins = 600 requests/hour
- 75% reduction in background load
- Admin dashboard feels snappier

Side Effects of Disabling:

❌ No autosave while writing posts
❌ Won’t see “User X is editing this post” warnings
❌ Comment moderation notifications delayed
✅ But: Admin dashboard 3-5x faster
✅ Server load reduced by 60-80%

Recommended Setup:

// Disable on frontend (visitors don't need it)
add_action('init', function() {
    if (!is_admin()) {
        wp_deregister_script('heartbeat');
    }
});

// Slow down in admin dashboard
add_filter('heartbeat_settings', function($settings) {
    $settings['interval'] = 60;
    return $settings;
});

// Keep normal speed in post editor (for autosave)
add_filter('heartbeat_settings', function($settings) {
    global $pagenow;
    if ($pagenow == 'post.php' || $pagenow == 'post-new.php') {
        $settings['interval'] = 15; // Keep fast for editing
    }
    return $settings;
});

Alternative: Use Plugin

Install “Heartbeat Control” plugin:
– GUI to control Heartbeat per page
– No code needed
– Can set different intervals for dashboard/frontend/editor

Check If Heartbeat Is The Problem:

Open browser DevTools → Network tab → Filter: “heartbeat”
If you see requests every 15 seconds consuming 200-500ms, it’s the culprit!

// Typical Heartbeat request:
POST /wp-admin/admin-ajax.php
Action: heartbeat
Response time: 250ms
Every 15 seconds

= Noticeable slowdown on slower servers