Challenge 1: Cache an Expensive Query — Possible Solution
====================================================================

// app/Http/Controllers/BookController.php

use Illuminate\Support\Facades\Cache;
use App\Models\Book;

public function stats()
{
    $stats = Cache::remember('book_stats', 600, function () {
        return [
            'total' => Book::count(),
            'average_price' => Book::avg('price'),
        ];
    });

    return view('books.stats', ['stats' => $stats]);
}

WHY THIS WORKS
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- Cache::remember('book_stats', 600, function () { ... }) checks for an
  existing 'book_stats' cache entry first; if it's missing or expired, it
  runs the closure ONCE, stores the result under that key for 600 seconds
  (10 minutes), and returns it — all in one call, exactly the same
  check-then-compute-then-store pattern as Django's cache.get_or_set().
- Within that 10-minute window, every subsequent call to
  Cache::remember('book_stats', ...) returns the cached array instantly
  without running Book::count() or Book::avg('price') again — those two
  separate database queries only actually execute roughly once every 10
  minutes, regardless of how many requests hit this method in between.
- The closure (function () { ... }) is only invoked if the cache is
  actually missing — Cache::remember() doesn't eagerly run it just to
  check whether its result should be discarded, mirroring exactly how
  Django's get_or_set() treats its callback argument.