Invalidate Caches Automatically by Touching Parent Timestamps with $touches

Define the $touches property on child models to update parent model updated_at timestamps automatically when child records change.

When caching parent model data or HTTP responses (such as caching a Post with its Comments), adding or updating a comment leaves the parent post's updated_at timestamp unchanged, resulting in stale cache hits.

Defining $touches on the child model updates parent timestamps automatically.

Configuring $touches on Child Models

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;

class Comment extends Model
{
    // List parent relationships to touch when this model is saved or deleted
    protected $touches = ['post'];

    public function post(): BelongsTo
    {
        return $this->belongsTo(Post::class);
    }
}

How It Works

When a comment is created, updated, or deleted:

$comment = Comment::find(1);
$comment->update(['content' => 'Updated comment text.']);

// The associated Post's updated_at timestamp is automatically set to now()!

Summary

• Automatically refreshes parent updated_at timestamps on child save and delete events.
• Essential for HTTP ETag generation and timestamp-based cache invalidation.
• Supports multiple parent relationship names in the array (['post', 'author']).