Cache Invalidation: Keeping Cached Data Correct

Caching speeds up your app, but stale cache can show wrong data. A professional caching strategy always answers one question:

    When does cached data become invalid?
    
    ## Pattern 1: Time-based expiration
    
    ```php
    Cache::remember('top_posts', 60, fn () => Post::top()->get());
    ```
    
    Simple, but not always accurate.
    
    ## Pattern 2: Forget cache when data changes
    
    ```php
    Post::created(function () {
      Cache::forget('top_posts');
    });
    ```
    
    ## Pattern 3: Versioned cache keys
    
    ```php
    $key = 'top_posts:v' . Cache::get('top_posts_version', 1);
    ```
    
    When posts update, bump the version.
    
    ## Graph: Invalidation flow
    
    ```mermaid
    flowchart TD
      A[Data Updated] --> B[Invalidate Cache]
      B --> C[Next Request Rebuilds Cache]
    ```
    
    In the next tutorial, we will implement file downloads and streaming large exports.