perf: cache account post count for 5 minutes in HasUsage

Posts have no plan-quota gating, so a brief staleness on the count is
acceptable. Avoids the heavy aggregate query on every authenticated
request. Empty-account case skips cache writes entirely.

app/Models/Traits/HasUsage.php

@@ -10,6 +10,8 @@
 use App\Features\WorkspaceLimit;
 use App\Models\AiUsageLog;
 use App\Models\Invite;
+use App\Models\Post;
+use Illuminate\Support\Facades\Cache;
 use Laravel\Pennant\Feature;
 
 /**
@@ -21,13 +23,21 @@
  */
 trait HasUsage
 {
+    /**
+     * Cache TTL for the per-account post count. Posts are unbounded by plan
+     * limits and not used for any quota gating, so a few minutes of staleness
+     * is acceptable in exchange for skipping a potentially heavy aggregate
+     * query on every authenticated request.
+     */
+    private const POST_COUNT_CACHE_TTL = 300;
+
     /**
      * @return array{workspaceCount: int, socialAccountCount: int, memberCount: int, pendingInviteCount: int, postCount: int, creditsUsed: int}
      */
     public function usage(): array
     {
         $workspaces = $this->workspaces()
-            ->withCount(['socialAccounts', 'posts'])
+            ->withCount('socialAccounts')
             ->get();
 
         return [
@@ -37,7 +47,7 @@ public function usage(): array
             'pendingInviteCount' => Invite::where('account_id', $this->id)
                 ->whereNull('accepted_at')
                 ->count(),
-            'postCount' => (int) $workspaces->sum('posts_count'),
+            'postCount' => $this->cachedPostCount($workspaces->pluck('id')->all()),
             'creditsUsed' => AiUsageLog::monthlyCredits($this->id),
         ];
     }
@@ -54,4 +64,20 @@ public function featureLimits(): array
             'monthlyCreditsLimit' => Feature::for($this)->value(MonthlyCreditsLimit::class),
         ];
     }
+
+    /**
+     * @param  array<int, string>  $workspaceIds
+     */
+    private function cachedPostCount(array $workspaceIds): int
+    {
+        if (empty($workspaceIds)) {
+            return 0;
+        }
+
+        return Cache::remember(
+            "account:{$this->id}:posts_count",
+            self::POST_COUNT_CACHE_TTL,
+            fn () => Post::whereIn('workspace_id', $workspaceIds)->count(),
+        );
+    }
 }

tests/Feature/Models/HasUsageTraitTest.php

@@ -5,9 +5,11 @@
 use App\Models\Account;
 use App\Models\Invite;
 use App\Models\Plan;
+use App\Models\Post;
 use App\Models\SocialAccount;
 use App\Models\User;
 use App\Models\Workspace;
+use Illuminate\Support\Facades\Cache;
 
 beforeEach(function () {
     $this->account = Account::factory()->create();
@@ -68,3 +70,37 @@
 
     expect($this->account->usage()['pendingInviteCount'])->toBe(1);
 });
+
+test('postCount is cached and survives new posts within the TTL', function () {
+    $workspace = Workspace::factory()->create([
+        'account_id' => $this->account->id,
+        'user_id' => $this->owner->id,
+    ]);
+
+    Post::factory()->count(2)->create([
+        'workspace_id' => $workspace->id,
+        'user_id' => $this->owner->id,
+    ]);
+
+    // First call primes the cache.
+    expect($this->account->usage()['postCount'])->toBe(2);
+
+    // A new post is created mid-window. The cached value should win.
+    Post::factory()->create([
+        'workspace_id' => $workspace->id,
+        'user_id' => $this->owner->id,
+    ]);
+
+    expect($this->account->usage()['postCount'])->toBe(2);
+
+    // Forgetting the cache key returns the fresh count.
+    Cache::forget("account:{$this->account->id}:posts_count");
+    expect($this->account->usage()['postCount'])->toBe(3);
+});
+
+test('postCount returns zero without querying when account has no workspaces', function () {
+    expect($this->account->usage()['postCount'])->toBe(0);
+
+    // No cache entry should be written for the empty case.
+    expect(Cache::has("account:{$this->account->id}:posts_count"))->toBeFalse();
+});