diff --git a/config/services.yaml b/config/services.yaml
index 8de680d..b4f0f26 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -23,6 +23,7 @@ services:
       - "../src/Entity/"
       - "../src/Kernel.php"
       - "../src/Service/Processes/"
+      - "../src/Service/Types/"
       - "../src/Twig/Components/Challenge/EventConstant.php"
 
   # add more service definitions when explicit configuration is needed
diff --git a/src/Entity/Question.php b/src/Entity/Question.php
index 83dda74..3474022 100644
--- a/src/Entity/Question.php
+++ b/src/Entity/Question.php
@@ -176,55 +176,6 @@ public function setSolutionVideo(?string $solution_video): static
         return $this;
     }
 
-    /**
-     * Get the pass rate of the question.
-     *
-     * @param Group|null $group the group to filter the attempts by (null = no group)
-     *
-     * @return float the pass rate of the question
-     */
-    public function getPassRate(?Group $group): float
-    {
-        $totalAttemptCount = $this->getTotalAttemptCount($group);
-        if (0 === $totalAttemptCount) {
-            return 0;
-        }
-
-        return round($this->getTotalSolvedCount($group) / $totalAttemptCount * 100, 2);
-    }
-
-    /**
-     * Get the total number of attempts made on the question.
-     *
-     * @param Group|null $group the group to filter the attempts by (null = no group)
-     *
-     * @return int the total number of attempts made on the question
-     */
-    public function getTotalAttemptCount(?Group $group): int
-    {
-        return $this->getSolutionEvents()
-            ->filter(fn (SolutionEvent $solutionEvent) => $group === $solutionEvent->getSubmitter()?->getGroup())
-            ->count();
-    }
-
-    /**
-     * Get the total number of times the question has been solved.
-     *
-     * @param Group|null $group the group to filter the attempts by (null = no group)
-     *
-     * @return int the total number of times the question has been solved
-     */
-    public function getTotalSolvedCount(?Group $group): int
-    {
-        return $this->getSolutionEvents()
-            ->filter(
-                fn (SolutionEvent $solutionEvent) => (
-                    SolutionEventStatus::Passed === $solutionEvent->getStatus()
-                        && $group === $solutionEvent->getSubmitter()?->getGroup()
-                )
-            )->count();
-    }
-
     /**
      * @return Collection<int, SolutionEvent>
      */
diff --git a/src/Repository/SolutionEventRepository.php b/src/Repository/SolutionEventRepository.php
index bc5d6ea..61b55b1 100644
--- a/src/Repository/SolutionEventRepository.php
+++ b/src/Repository/SolutionEventRepository.php
@@ -189,4 +189,34 @@ public function listLeaderboard(?Group $group, string $interval): array
 
         return $leaderboard;
     }
+
+    /**
+     * Get the total attempts made on the question.
+     *
+     * @param Question   $question the question to query
+     * @param Group|null $group    the group to filter the attempts by (null = no group)
+     *
+     * @return SolutionEvent[] the total attempts made on the question
+     */
+    public function getTotalAttempts(Question $question, ?Group $group): array
+    {
+        $qb = $this->createQueryBuilder('se')
+            ->join('se.submitter', 'submitter')
+            ->where('se.question = :question')
+            ->setParameter('question', $question);
+
+        if ($group) {
+            $qb->andWhere('submitter.group = :group')
+                ->setParameter('group', $group);
+        } else {
+            $qb->andWhere('submitter.group IS NULL');
+        }
+
+        /**
+         * @var SolutionEvent[] $result
+         */
+        $result = $qb->getQuery()->getResult();
+
+        return $result;
+    }
 }
diff --git a/src/Service/PassRateService.php b/src/Service/PassRateService.php
new file mode 100644
index 0000000..db696c2
--- /dev/null
+++ b/src/Service/PassRateService.php
@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service;
+
+use App\Entity\Group;
+use App\Entity\Question;
+use App\Repository\SolutionEventRepository;
+use App\Service\Types\PassRate;
+
+/**
+ * Get the pass rate of a question in the optimized matter.
+ */
+readonly class PassRateService
+{
+    public function __construct(
+        private SolutionEventRepository $solutionEventRepository,
+    ) {
+    }
+
+    /**
+     * Get the pass rate in this group of a question.
+     *
+     * @param Question   $question the question to calculate the pass rate
+     * @param Group|null $group    the group to calculate the pass rate, null for no group
+     *
+     * @return PassRate the pass rate, see {@link PassRate} for details
+     */
+    public function getPassRate(Question $question, ?Group $group): PassRate
+    {
+        $attempts = $this->solutionEventRepository->getTotalAttempts($question, $group);
+
+        return new PassRate($attempts);
+    }
+}
diff --git a/src/Service/Types/PassRate.php b/src/Service/Types/PassRate.php
new file mode 100644
index 0000000..067d080
--- /dev/null
+++ b/src/Service/Types/PassRate.php
@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service\Types;
+
+use App\Entity\SolutionEvent;
+use App\Entity\SolutionEventStatus;
+
+/**
+ * The pass rate of a question.
+ *
+ * - `total`: the total number of attempts
+ * - `passed`: the number of successful attempts
+ * - `passRate`: the pass rate of the question in percentage
+ * - `level`: the level of the pass rate, can be 'low', 'medium', or 'high'
+ */
+readonly class PassRate
+{
+    /**
+     * @var int the total number of attempts
+     */
+    public int $total;
+
+    /**
+     * @var int the number of successful attempts
+     */
+    public int $passed;
+
+    /**
+     * @param SolutionEvent[] $attempts
+     */
+    public function __construct(
+        array $attempts,
+    ) {
+        $this->total = \count($attempts);
+        $this->passed = \count(array_filter($attempts, fn (SolutionEvent $event) => SolutionEventStatus::Passed == $event->getStatus()));
+    }
+
+    /**
+     * Calculate the pass rate of a question.
+     *
+     * @return float the pass rate of the question in percentage
+     */
+    public function getPassRate(): float
+    {
+        if (0 === $this->total) {
+            return 0;
+        }
+
+        return round($this->passed / $this->total * 100, 2);
+    }
+
+    /**
+     * @return string the level of the pass rate, can be 'low', 'medium', or 'high'
+     */
+    public function getLevel(): string
+    {
+        $passRate = $this->getPassRate();
+
+        return match (true) {
+            $passRate <= 40 => 'low',
+            $passRate <= 70 => 'medium',
+            default => 'high',
+        };
+    }
+}
diff --git a/src/Twig/Components/Challenge/Header.php b/src/Twig/Components/Challenge/Header.php
index a7f1781..18750b4 100644
--- a/src/Twig/Components/Challenge/Header.php
+++ b/src/Twig/Components/Challenge/Header.php
@@ -9,6 +9,8 @@
 use App\Entity\User;
 use App\Repository\QuestionRepository;
 use App\Repository\SolutionEventRepository;
+use App\Service\PassRateService;
+use App\Service\Types\PassRate;
 use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
 
 #[AsTwigComponent]
@@ -21,6 +23,7 @@ final class Header
     public function __construct(
         private readonly SolutionEventRepository $solutionEventRepository,
         private readonly QuestionRepository $questionRepository,
+        private readonly PassRateService $passRateService,
     ) {
     }
 
@@ -42,4 +45,9 @@ public function getPreviousPage(): ?int
     {
         return $this->questionRepository->getPreviousPage($this->question->getId());
     }
+
+    public function getPassRate(): PassRate
+    {
+        return $this->passRateService->getPassRate($this->question, $this->user->getGroup());
+    }
 }
diff --git a/src/Twig/Components/Questions/Card.php b/src/Twig/Components/Questions/Card.php
index 3effae4..a5b121d 100644
--- a/src/Twig/Components/Questions/Card.php
+++ b/src/Twig/Components/Questions/Card.php
@@ -6,6 +6,8 @@
 
 use App\Entity\Question;
 use App\Entity\User;
+use App\Service\PassRateService;
+use App\Service\Types\PassRate;
 use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
 
 #[AsTwigComponent]
@@ -14,21 +16,16 @@ final class Card
     public Question $question;
     public User $currentUser;
 
+    public function __construct(
+        private readonly PassRateService $passRateService,
+    ) {
+    }
+
     /**
-     * Get the pass rate level of the question.
-     *
-     * Low: 0% - 40%
-     * Medium: 41 – 70%
-     * High: 71% - 100%
+     * Get the pass rate of the question.
      */
-    public function getPassRateLevel(): string
+    public function getPassRate(): PassRate
     {
-        $passRate = $this->question->getPassRate($this->currentUser->getGroup());
-
-        return match (true) {
-            $passRate <= 40 => 'low',
-            $passRate <= 70 => 'medium',
-            default => 'high',
-        };
+        return $this->passRateService->getPassRate($this->question, $this->currentUser->getGroup());
     }
 }
diff --git a/templates/components/Challenge/Header.html.twig b/templates/components/Challenge/Header.html.twig
index 7f4d167..eb8a9c8 100644
--- a/templates/components/Challenge/Header.html.twig
+++ b/templates/components/Challenge/Header.html.twig
@@ -5,10 +5,11 @@
         <li class="challenge-header__lists__type">{{ question.type }}</li>
         <li class="challenge-header__lists__pass_rate">
             通過率
+            {% set passRate = this.passRate %}
             <a class="challenge-header__lists__pass_rate__value" href="#" rel="help" data-bs-toggle="tooltip"
                data-bs-placement="bottom"
-               data-bs-title="{{ question.totalAttemptCount(user.group) }} 次挑戰中有 {{ question.totalSolvedCount(user.group) }} 次成功">
-                {{ question.passRate(user.group) }}%
+               data-bs-title="{{ passRate.total }} 次挑戰中有 {{ passRate.passed }} 次成功">
+                {{ passRate.passRate }}%
             </a>
         </li>
     </ul>
diff --git a/templates/components/Questions/Card.html.twig b/templates/components/Questions/Card.html.twig
index 30659a0..35433aa 100644
--- a/templates/components/Questions/Card.html.twig
+++ b/templates/components/Questions/Card.html.twig
@@ -11,7 +11,8 @@
 
             <div class="question-card__operations">
                 <a role="button" class="btn btn-primary" href="{{ path('app_challenge', {id: question.id}) }}">進行測驗</a>
-                <div class="question-card__pass-rate" data-pass-rate="{{ this.passRateLevel }}">通過率 {{ question.passRate(currentUser.group) }}%</div>
+                {% set passRate = this.passRate %}
+                <div class="question-card__pass-rate" data-pass-rate="{{ passRate.level }}">通過率 {{ passRate.passRate }}%</div>
             </div>
 
             <div class="question-card__background">