diff --git a/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarConnection.java b/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarConnection.java
index ecb5992c..1cbf7bdc 100644
--- a/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarConnection.java
+++ b/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarConnection.java
@@ -17,6 +17,8 @@
 import lombok.Builder;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
 
 @Entity
 @Table(name = "calendar_connections")
diff --git a/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarRevocationOutbox.java b/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarRevocationOutbox.java
index 26c16848..72723ae8 100644
--- a/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarRevocationOutbox.java
+++ b/src/main/java/com/Timo/Timo/domain/calendar/entity/CalendarRevocationOutbox.java
@@ -53,4 +53,4 @@ public void markFailed() {
       this.status = RevocationStatus.FAILED;
     }
   }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/com/Timo/Timo/domain/calendar/repository/CalendarConnectionRepository.java b/src/main/java/com/Timo/Timo/domain/calendar/repository/CalendarConnectionRepository.java
index 5ef2ec9f..4c3e171f 100644
--- a/src/main/java/com/Timo/Timo/domain/calendar/repository/CalendarConnectionRepository.java
+++ b/src/main/java/com/Timo/Timo/domain/calendar/repository/CalendarConnectionRepository.java
@@ -3,9 +3,18 @@
 import com.Timo.Timo.domain.calendar.entity.CalendarConnection;
 import java.util.Optional;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 public interface CalendarConnectionRepository extends JpaRepository<CalendarConnection, Long> {
 
   Optional<CalendarConnection> findByUserId(Long userId);
   boolean existsByUserId(Long userId);
+
+  @Query("""
+		select coalesce(c.refreshToken, c.accessToken)
+		from CalendarConnection c
+		where c.user.id = :userId
+		""")
+  Optional<String> findTokenToRevokeByUserId(@Param("userId") Long userId);
 }
diff --git a/src/main/java/com/Timo/Timo/domain/tag/entity/Tag.java b/src/main/java/com/Timo/Timo/domain/tag/entity/Tag.java
index 823df099..f10ec676 100644
--- a/src/main/java/com/Timo/Timo/domain/tag/entity/Tag.java
+++ b/src/main/java/com/Timo/Timo/domain/tag/entity/Tag.java
@@ -15,6 +15,8 @@
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
 
 @Entity
 @Table(name = "tags",
@@ -33,7 +35,8 @@ public class Tag {
 
 	@ManyToOne(fetch = FetchType.LAZY)
 	@JoinColumn(name = "user_id")
-	private User user;
+  @OnDelete(action = OnDeleteAction.CASCADE)
+  private User user;
 
 	@Column(name = "name", nullable = false, length = 10)
 	private String name;
diff --git a/src/main/java/com/Timo/Timo/domain/timer/entity/TimerRecord.java b/src/main/java/com/Timo/Timo/domain/timer/entity/TimerRecord.java
index 65dc80f4..d58bedeb 100644
--- a/src/main/java/com/Timo/Timo/domain/timer/entity/TimerRecord.java
+++ b/src/main/java/com/Timo/Timo/domain/timer/entity/TimerRecord.java
@@ -25,6 +25,8 @@
 import lombok.Builder;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
 import org.springframework.data.annotation.CreatedDate;
 import org.springframework.data.jpa.domain.support.AuditingEntityListener;
 
@@ -42,10 +44,12 @@ public class TimerRecord {
 
   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "user_id", nullable = false)
+  @OnDelete(action = OnDeleteAction.CASCADE)
   private User user;
 
   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "todo_id", nullable = false)
+  @OnDelete(action = OnDeleteAction.CASCADE)
   private Todo todo;
 
   @Column(name = "planned_seconds", nullable = false)
diff --git a/src/main/java/com/Timo/Timo/domain/timer/entity/TimerSession.java b/src/main/java/com/Timo/Timo/domain/timer/entity/TimerSession.java
index e29ef9cd..d42ddbd8 100644
--- a/src/main/java/com/Timo/Timo/domain/timer/entity/TimerSession.java
+++ b/src/main/java/com/Timo/Timo/domain/timer/entity/TimerSession.java
@@ -16,6 +16,8 @@
 import lombok.Builder;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
 
 @Entity
 @Table(name = "timer_sessions")
@@ -30,6 +32,7 @@ public class TimerSession {
 
   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "timer_record_id", nullable = false)
+  @OnDelete(action = OnDeleteAction.CASCADE)
   private TimerRecord timerRecord;
 
   @Column(name = "started_at", nullable = false)
diff --git a/src/main/java/com/Timo/Timo/domain/todo/entity/Subtask.java b/src/main/java/com/Timo/Timo/domain/todo/entity/Subtask.java
index 4a6f1b95..f5af0315 100644
--- a/src/main/java/com/Timo/Timo/domain/todo/entity/Subtask.java
+++ b/src/main/java/com/Timo/Timo/domain/todo/entity/Subtask.java
@@ -14,6 +14,8 @@
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
 
 @Entity
 @Table(name = "subtasks")
@@ -28,7 +30,8 @@ public class Subtask extends BaseTimeEntity {
 
 	@ManyToOne(fetch = FetchType.LAZY, optional = false)
 	@JoinColumn(name = "todo_id", nullable = false)
-	private Todo todo;
+  @OnDelete(action = OnDeleteAction.CASCADE)
+  private Todo todo;
 
 	@Column(name = "content", nullable = false, length = 20)
 	private String content;
diff --git a/src/main/java/com/Timo/Timo/domain/todo/entity/Todo.java b/src/main/java/com/Timo/Timo/domain/todo/entity/Todo.java
index a887da03..1d4a27d9 100644
--- a/src/main/java/com/Timo/Timo/domain/todo/entity/Todo.java
+++ b/src/main/java/com/Timo/Timo/domain/todo/entity/Todo.java
@@ -36,6 +36,8 @@
 import lombok.Builder;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
 
 @Entity
 @Table(name = "todos")
@@ -50,7 +52,8 @@ public class Todo extends BaseTimeEntity {
 
 	@ManyToOne(fetch = FetchType.LAZY, optional = false)
 	@JoinColumn(name = "user_id", nullable = false)
-	private User user;
+  @OnDelete(action = OnDeleteAction.CASCADE)
+  private User user;
 
 	@Enumerated(EnumType.STRING)
 	@Column(name = "icon", length = 20)
diff --git a/src/main/java/com/Timo/Timo/domain/todo/entity/TodoInstance.java b/src/main/java/com/Timo/Timo/domain/todo/entity/TodoInstance.java
index a8692ed5..8a6c2fb4 100644
--- a/src/main/java/com/Timo/Timo/domain/todo/entity/TodoInstance.java
+++ b/src/main/java/com/Timo/Timo/domain/todo/entity/TodoInstance.java
@@ -20,6 +20,8 @@
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
 
 @Entity
 @Table(
@@ -40,6 +42,7 @@ public class TodoInstance extends BaseTimeEntity {
 
     @ManyToOne(fetch = FetchType.LAZY, optional = false)
     @JoinColumn(name = "todo_id", nullable = false)
+    @OnDelete(action = OnDeleteAction.CASCADE)
     private Todo todo;
 
     @Column(name = "instance_date", nullable = false)
diff --git a/src/main/java/com/Timo/Timo/global/auth/service/AuthService.java b/src/main/java/com/Timo/Timo/global/auth/service/AuthService.java
index 0560f9cc..6f1db3cb 100644
--- a/src/main/java/com/Timo/Timo/global/auth/service/AuthService.java
+++ b/src/main/java/com/Timo/Timo/global/auth/service/AuthService.java
@@ -129,16 +129,13 @@ public void afterCommit() {
   }
 
   private void revokeCalendarConnectionIfExists(Long userId) {
-    calendarConnectionRepository.findByUserId(userId).ifPresent(connection -> {
-      String tokenToRevoke = connection.getRefreshToken() != null
-          ? connection.getRefreshToken()
-          : connection.getAccessToken();
-
-      calendarRevocationOutboxRepository.save(
-          CalendarRevocationOutbox.builder()
-              .token(tokenToRevoke)
-              .build()
-      );
-    });
+    calendarConnectionRepository.findTokenToRevokeByUserId(userId)
+        .ifPresent(tokenToRevoke ->
+            calendarRevocationOutboxRepository.save(
+                CalendarRevocationOutbox.builder()
+                    .token(tokenToRevoke)
+                    .build()
+            )
+        );
   }
 }