[REFACTOR] 알림 조회 redis 캐싱 추가

src/main/java/com/example/RealMatch/notification/application/service/NotificationQueryService.java

@@ -18,6 +18,7 @@
 import com.example.RealMatch.notification.domain.entity.enums.NotificationKind;
 import com.example.RealMatch.notification.domain.repository.NotificationRepository;
 import com.example.RealMatch.notification.exception.NotificationErrorCode;
+import com.example.RealMatch.notification.infrastructure.redis.NotificationUnreadCountCache;
 import com.example.RealMatch.notification.presentation.dto.response.NotificationDateGroup;
 import com.example.RealMatch.notification.presentation.dto.response.NotificationListResponse;
 import com.example.RealMatch.notification.presentation.dto.response.NotificationResponse;
@@ -30,6 +31,7 @@
 public class NotificationQueryService {
 
     private final NotificationRepository notificationRepository;
+    private final NotificationUnreadCountCache unreadCountCache;
 
     private static final DateTimeFormatter DATE_LABEL_FORMATTER =
             DateTimeFormatter.ofPattern("yy.MM.dd (E)", Locale.KOREAN);
@@ -52,7 +54,7 @@ public NotificationListResponse getNotifications(Long userId, String filter, int
 
         List<NotificationDateGroup> groups = buildDateGroups(notificationPage.getContent());
 
-        long unreadCount = notificationRepository.countUnreadByUserId(userId);
+        long unreadCount = getUnreadCount(userId);
 
         return new NotificationListResponse(
                 items,
@@ -66,7 +68,12 @@ public NotificationListResponse getNotifications(Long userId, String filter, int
     }
 
     public long getUnreadCount(Long userId) {
-        return notificationRepository.countUnreadByUserId(userId);
+        return unreadCountCache.get(userId)
+                .orElseGet(() -> {
+                    long count = notificationRepository.countUnreadByUserId(userId);
+                    unreadCountCache.set(userId, count);
+                    return count;
+                });
     }
 
     private List<NotificationKind> resolveKinds(String filter) {

src/main/java/com/example/RealMatch/notification/application/service/NotificationService.java

@@ -22,6 +22,7 @@
 import com.example.RealMatch.notification.domain.repository.NotificationOutboxRepository;
 import com.example.RealMatch.notification.domain.repository.NotificationRepository;
 import com.example.RealMatch.notification.exception.NotificationErrorCode;
+import com.example.RealMatch.notification.infrastructure.redis.NotificationUnreadCountCache;
 import com.example.RealMatch.user.domain.entity.enums.NotificationChannel;
 
 import lombok.RequiredArgsConstructor;
@@ -42,6 +43,7 @@ public class NotificationService {
     private final NotificationDeliveryRepository notificationDeliveryRepository;
     private final NotificationOutboxRepository notificationOutboxRepository;
     private final NotificationChannelResolver channelResolver;
+    private final NotificationUnreadCountCache unreadCountCache;
 
     @Transactional(propagation = Propagation.REQUIRES_NEW)
     public Notification create(CreateNotificationCommand command) {
@@ -64,6 +66,8 @@ public Notification create(CreateNotificationCommand command) {
                 command.getEventId(),
                 command.getUserId());
 
+        unreadCountCache.invalidateAfterCommit(command.getUserId());
+
         return savedNotification;
     }
 
@@ -112,15 +116,19 @@ private String generateIdempotencyKey(String eventId, NotificationKind kind,
     public void markAsRead(Long userId, UUID notificationId) {
         Notification notification = findNotificationForUser(userId, notificationId);
         notification.markAsRead();
+        unreadCountCache.invalidateAfterCommit(userId);
     }
 
     public int markAllAsRead(Long userId) {
-        return notificationRepository.markAllAsRead(userId);
+        int count = notificationRepository.markAllAsRead(userId);
+        unreadCountCache.invalidateAfterCommit(userId);
+        return count;
     }
 
     public void softDelete(Long userId, UUID notificationId) {
         Notification notification = findNotificationForUser(userId, notificationId);
         notification.softDelete();
+        unreadCountCache.invalidateAfterCommit(userId);
     }
 
     private Notification findNotificationForUser(Long userId, UUID notificationId) {

src/main/java/com/example/RealMatch/notification/infrastructure/redis/NotificationUnreadCountCache.java

@@ -0,0 +1,95 @@
+package com.example.RealMatch.notification.infrastructure.redis;
+
+import java.time.Duration;
+import java.util.OptionalLong;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.data.redis.core.StringRedisTemplate;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.support.TransactionSynchronization;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+import lombok.RequiredArgsConstructor;
+
+/**
+ * 미읽음 알림 개수 조회 성능 최적화를 위한 Redis 캐시.
+ * <p>캐시 키: notification:unread:{userId}
+ * <p>캐시 무효화: 알림 생성, 읽음 처리, 전체 읽기, 소프트 삭제 시 호출
+ * <p>Redis 장애 시 DB 조회로 폴백
+ */
+@Component
+@RequiredArgsConstructor
+public class NotificationUnreadCountCache {
+
+    private static final Logger LOG = LoggerFactory.getLogger(NotificationUnreadCountCache.class);
+    private static final String KEY_PREFIX = "notification:unread:";
+    private static final Duration TTL = Duration.ofMinutes(10);
+
+    private final StringRedisTemplate redisTemplate;
+
+    public OptionalLong get(Long userId) {
+        if (userId == null) {
+            return OptionalLong.empty();
+        }
+        try {
+            String key = KEY_PREFIX + userId;
+            String value = redisTemplate.opsForValue().get(key);
+            if (value == null) {
+                return OptionalLong.empty();
+            }
+            return OptionalLong.of(Long.parseLong(value));
+        } catch (NumberFormatException e) {
+            invalidate(userId);
+            return OptionalLong.empty();
+        } catch (Exception e) {
+            LOG.warn("[UnreadCountCache] Redis get failed, fallback to DB. userId={}", userId, e);
+            return OptionalLong.empty();
+        }
+    }
+
+    public void set(Long userId, long count) {
+        if (userId == null) {
+            return;
+        }
+        try {
+            redisTemplate.opsForValue().set(KEY_PREFIX + userId, String.valueOf(count), TTL);
+        } catch (Exception e) {
+            LOG.warn("[UnreadCountCache] Redis set failed. userId={}", userId, e);
+        }
+    }
+
+    public void invalidate(Long userId) {
+        if (userId == null) {
+            return;
+        }
+        try {
+            redisTemplate.delete(KEY_PREFIX + userId);
+        } catch (Exception e) {
+            LOG.warn("[UnreadCountCache] Redis invalidate failed. userId={}", userId, e);
+        }
+    }
+
+    /**
+     * 트랜잭션 커밋 완료 후 캐시를 무효화합니다.
+     * <p>커밋 이전 무효화 시 다른 스레드가 아직 커밋되지 않은 DB 값을 읽어
+     * 캐시에 저장하는 레이스 컨디션을 방지합니다.
+     */
+    public void invalidateAfterCommit(Long userId) {
+        if (userId == null) {
+            return;
+        }
+        if (TransactionSynchronizationManager.isSynchronizationActive()) {
+            TransactionSynchronizationManager.registerSynchronization(
+                    new TransactionSynchronization() {
+                        @Override
+                        public void afterCommit() {
+                            invalidate(userId);
+                        }
+                    }
+            );
+        } else {
+            invalidate(userId);
+        }
+    }
+}