@@ -0,0 +1,71 @@
+package hanghaeplus.signupforlecture.application.lecture.facade;
+
+import hanghaeplus.signupforlecture.application.lecture.domain.model.Lecture;
+import hanghaeplus.signupforlecture.application.lecture.domain.model.LectureCapacity;
+import hanghaeplus.signupforlecture.application.lecture.dto.request.LectureApplyRequestDto;
+import hanghaeplus.signupforlecture.application.lecture.dto.request.LectureAvailableRequestDto;
+import hanghaeplus.signupforlecture.application.lecture.dto.response.LectureAvailableResponseDto;
+import hanghaeplus.signupforlecture.application.lecture.dto.response.LectureSignedUpResponseDto;
+import hanghaeplus.signupforlecture.application.lecture.service.LectureApplyHistoryService;
+import hanghaeplus.signupforlecture.application.lecture.service.LectureCapacityService;
+import hanghaeplus.signupforlecture.application.lecture.service.LectureService;
+import hanghaeplus.signupforlecture.application.user.domain.model.User;
+import hanghaeplus.signupforlecture.application.user.service.UserService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Isolation;
+import org.springframework.transaction.annotation.Propagation;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+@Component
+@RequiredArgsConstructor
+public class LectureFacade {
+
+    private final UserService userService;
+
+    private final LectureService lectureService;
+    private final LectureApplyHistoryService lectureApplyHistoryService;
+    private final LectureCapacityService lectureCapacityService;
+
+    public List<LectureAvailableResponseDto> getAvailableLectures(LectureAvailableRequestDto lectureAvailableRequestDto) {
+        List<Lecture> availableLectureIds = lectureService.getAvailableLectures(lectureAvailableRequestDto.requestDate());
+        List<LectureCapacity> availableLectures = lectureCapacityService.getAvailableSlot(availableLectureIds);
+
+        return LectureAvailableResponseDto.fromDomains(availableLectureIds, availableLectures);
+    }
+
+    @Transactional
+    public void applyLecture(Long lectureId, LectureApplyRequestDto lectureApplyRequestDto) {
+        User user = userService.getUser(lectureApplyRequestDto.userId());
+        Lecture lecture = lectureService.getLecture(lectureId);
+
+        try {
+            // 중복 체크 (history 테이블)
+            lectureApplyHistoryService.checkApplyLectureHistory(lecture.id(), user.id());
+
+            // 신청 가능한 Slot (lectureCapacity 테이블) 조회 <락 획득>
+            LectureCapacity lectureCapacity = lectureCapacityService.getAvailableSlotLock(lecture.id());
+
+            // 내역 저장 (history 테이블)
+            lectureApplyHistoryService.insertAppliedHistory(lecture, user.id());
+
+            // 신청 가능 Slot - 1 로직 >> 저장 (lectureCapacity 테이블)
+            lectureCapacityService.applyAvailableSlot(lectureCapacity);
+        } catch (RuntimeException e) {
+            lectureApplyHistoryService.insertFailedHistory(lecture, user.id());
+        }
+    }
+
+    public List<LectureSignedUpResponseDto> getSignedUpLectures(Long userId) {
+        User user = userService.getUser(userId);
+
+        List<Long> signedUpLectureIds = lectureApplyHistoryService.findSignedUpLectureHistories(user.id());
+        List<Lecture> signedUpLectures = lectureService.findSignedUpLectures(signedUpLectureIds);
+
+        return signedUpLectures.stream()
+                .map(LectureSignedUpResponseDto::fromDomain)
+                .toList();
+    }
+}

리뷰: 정확한 이유는 모르겠지만 해당 락 획득 코드가 메서드 최상단으로 올라가면 `fail_applyLecture2` 테스트가 정상 진행이 됩니다!