diff --git a/backend-java/src/main/java/com/tasteby/controller/ChannelController.java b/backend-java/src/main/java/com/tasteby/controller/ChannelController.java
index 933790b..eec618a 100644
--- a/backend-java/src/main/java/com/tasteby/controller/ChannelController.java
+++ b/backend-java/src/main/java/com/tasteby/controller/ChannelController.java
@@ -7,6 +7,7 @@ import com.tasteby.security.AuthUtil;
 import com.tasteby.service.CacheService;
 import com.tasteby.service.ChannelService;
 import com.tasteby.service.YouTubeService;
+import org.springframework.dao.DataIntegrityViolationException;
 import org.springframework.http.HttpStatus;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.server.ResponseStatusException;
@@ -52,15 +53,20 @@ public class ChannelController {
         String channelId = body.get("channel_id");
         String channelName = body.get("channel_name");
         String titleFilter = body.get("title_filter");
+        // #295 — body 필수값 가드 (NOT NULL 컬럼에 빈 값 들어가 500 나는 것 방지)
+        if (channelId == null || channelId.isBlank()) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "channel_id는 필수입니다");
+        }
+        if (channelName == null || channelName.isBlank()) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "channel_name은 필수입니다");
+        }
         try {
             String id = channelService.create(channelId, channelName, titleFilter);
             cache.flush();
             return Map.of("id", id, "channel_id", channelId);
-        } catch (Exception e) {
-            if (e.getMessage() != null && e.getMessage().toUpperCase().contains("UQ_CHANNELS_CID")) {
-                throw new ResponseStatusException(HttpStatus.CONFLICT, "Channel already exists");
-            }
-            throw e;
+        } catch (DataIntegrityViolationException e) {
+            // #295 — 유니크 충돌을 메시지 문자열 매칭 대신 typed 예외로 감지 (제약명 변경에도 견고).
+            throw new ResponseStatusException(HttpStatus.CONFLICT, "Channel already exists");
         }
     }
 
diff --git a/backend-java/src/main/java/com/tasteby/controller/RestaurantController.java b/backend-java/src/main/java/com/tasteby/controller/RestaurantController.java
index 5eedee9..7640f25 100644
--- a/backend-java/src/main/java/com/tasteby/controller/RestaurantController.java
+++ b/backend-java/src/main/java/com/tasteby/controller/RestaurantController.java
@@ -7,6 +7,7 @@ import com.tasteby.security.AuthUtil;
 import com.tasteby.service.CacheService;
 import com.tasteby.service.GeocodingService;
 import com.tasteby.service.RestaurantService;
+import jakarta.annotation.PreDestroy;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.http.HttpStatus;
@@ -47,6 +48,12 @@ public class RestaurantController {
         this.objectMapper = objectMapper;
     }
 
+    // #290 — Bean 종료 시 virtual thread executor를 정리하여 리소스 누수 방지.
+    @PreDestroy
+    public void shutdownExecutor() {
+        executor.shutdown();
+    }
+
     @GetMapping
     public List<Restaurant> list(
             @RequestParam(defaultValue = "100") int limit,
@@ -61,7 +68,7 @@ public class RestaurantController {
         if (cached != null) {
             try {
                 return objectMapper.readValue(cached, new TypeReference<List<Restaurant>>() {});
-            } catch (Exception ignored) {}
+            } catch (Exception e) { log.warn("Cache deserialize failed, evicting: {}", e.getMessage()); cache.del(key); }
         }
         var result = restaurantService.findAll(limit, offset, cuisine, region, channel);
         cache.set(key, result);
@@ -75,7 +82,7 @@ public class RestaurantController {
         if (cached != null) {
             try {
                 return objectMapper.readValue(cached, Restaurant.class);
-            } catch (Exception ignored) {}
+            } catch (Exception e) { log.warn("Cache deserialize failed, evicting: {}", e.getMessage()); cache.del(key); }
         }
         var r = restaurantService.findById(id);
         if (r == null) throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Restaurant not found");
@@ -241,6 +248,10 @@ public class RestaurantController {
         var r = restaurantService.findById(id);
         if (r == null) throw new ResponseStatusException(HttpStatus.NOT_FOUND);
         String url = body.get("tabling_url");
+        // #290 — javascript:/외부 악성 URL 차단. 빈 문자열은 매핑 해제로 허용.
+        if (url != null && !url.isBlank() && !url.startsWith("https://tabling.co.kr/")) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "테이블링 URL은 https://tabling.co.kr/ 만 허용");
+        }
         restaurantService.update(id, Map.of("tabling_url", url != null ? url : ""));
         cache.flush();
         return Map.of("ok", true);
@@ -367,6 +378,12 @@ public class RestaurantController {
         var r = restaurantService.findById(id);
         if (r == null) throw new ResponseStatusException(HttpStatus.NOT_FOUND);
         String url = body.get("catchtable_url");
+        // #290 — javascript:/외부 악성 URL 차단. 빈 문자열은 매핑 해제로 허용.
+        if (url != null && !url.isBlank()
+                && !url.startsWith("https://app.catchtable.co.kr/")
+                && !url.startsWith("https://www.catchtable.co.kr/")) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "캐치테이블 URL은 https://(app|www).catchtable.co.kr/ 만 허용");
+        }
         restaurantService.update(id, Map.of("catchtable_url", url != null ? url : ""));
         cache.flush();
         return Map.of("ok", true);
@@ -379,7 +396,7 @@ public class RestaurantController {
         if (cached != null) {
             try {
                 return objectMapper.readValue(cached, new TypeReference<List<Map<String, Object>>>() {});
-            } catch (Exception ignored) {}
+            } catch (Exception e) { log.warn("Cache deserialize failed, evicting: {}", e.getMessage()); cache.del(key); }
         }
         var r = restaurantService.findById(id);
         if (r == null) throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Restaurant not found");
diff --git a/backend-java/src/main/java/com/tasteby/controller/ReviewController.java b/backend-java/src/main/java/com/tasteby/controller/ReviewController.java
index a905912..2bb1cf9 100644
--- a/backend-java/src/main/java/com/tasteby/controller/ReviewController.java
+++ b/backend-java/src/main/java/com/tasteby/controller/ReviewController.java
@@ -39,7 +39,7 @@ public class ReviewController {
             @PathVariable String restaurantId,
             @RequestBody Map<String, Object> body) {
         String userId = AuthUtil.getUserId();
-        double rating = ((Number) body.get("rating")).doubleValue();
+        double rating = requireRating(body.get("rating"));
         String text = (String) body.get("review_text");
         LocalDate visitedAt = body.get("visited_at") != null
                 ? LocalDate.parse((String) body.get("visited_at")) : null;
@@ -51,8 +51,7 @@ public class ReviewController {
             @PathVariable String reviewId,
             @RequestBody Map<String, Object> body) {
         String userId = AuthUtil.getUserId();
-        Double rating = body.get("rating") != null
-                ? ((Number) body.get("rating")).doubleValue() : null;
+        Double rating = body.get("rating") != null ? requireRating(body.get("rating")) : null;
         String text = (String) body.get("review_text");
         LocalDate visitedAt = body.get("visited_at") != null
                 ? LocalDate.parse((String) body.get("visited_at")) : null;
@@ -94,4 +93,18 @@ public class ReviewController {
     public List<Restaurant> myFavorites() {
         return reviewService.getUserFavorites(AuthUtil.getUserId());
     }
+
+    /**
+     * #294 — rating 검증: null/비숫자/범위 외 입력은 400.
+     */
+    private static double requireRating(Object raw) {
+        if (!(raw instanceof Number n)) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "rating은 숫자여야 합니다");
+        }
+        double v = n.doubleValue();
+        if (v < 0.0 || v > 5.0 || Double.isNaN(v)) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "rating은 0.0 ~ 5.0 범위여야 합니다");
+        }
+        return v;
+    }
 }
diff --git a/backend-java/src/main/java/com/tasteby/service/CacheService.java b/backend-java/src/main/java/com/tasteby/service/CacheService.java
index d92728e..f2dba58 100644
--- a/backend-java/src/main/java/com/tasteby/service/CacheService.java
+++ b/backend-java/src/main/java/com/tasteby/service/CacheService.java
@@ -85,4 +85,14 @@ public class CacheService {
             log.debug("Cache flush error: {}", e.getMessage());
         }
     }
+
+    // #290 — 단일 키 삭제 (캐시 역직렬화 실패 시 자동 evict 등에 사용)
+    public void del(String key) {
+        if (disabled) return;
+        try {
+            redis.delete(key);
+        } catch (Exception e) {
+            log.debug("Cache del error: {}", e.getMessage());
+        }
+    }
 }
diff --git a/backend-java/src/main/java/com/tasteby/service/ChannelService.java b/backend-java/src/main/java/com/tasteby/service/ChannelService.java
index 3240c41..8179370 100644
--- a/backend-java/src/main/java/com/tasteby/service/ChannelService.java
+++ b/backend-java/src/main/java/com/tasteby/service/ChannelService.java
@@ -27,11 +27,16 @@ public class ChannelService {
     }
 
     public boolean deactivate(String channelId) {
-        // Try deactivate by channel_id first, then by DB id
-        int rows = mapper.deactivateByChannelId(channelId);
-        if (rows == 0) {
-            rows = mapper.deactivateById(channelId);
-        }
+        if (channelId == null || channelId.isBlank()) return false;
+        // #295 — 입력 형식으로 명시적 분기:
+        //   "UC..."(24 chars) 형식 → YouTube channel_id로 비활성화
+        //   그 외(32-char hex UUID 등) → DB id로 비활성화
+        // 이전: channel_id 시도 → 0이면 id 시도. 우연히 UC가 hex와 같을 확률은 0이지만
+        // 가독성/의도 명확성 + 잘못된 폴백 차단을 위해 명시화.
+        boolean looksLikeYouTubeId = channelId.startsWith("UC") && channelId.length() == 24;
+        int rows = looksLikeYouTubeId
+                ? mapper.deactivateByChannelId(channelId)
+                : mapper.deactivateById(channelId);
         return rows > 0;
     }
 
diff --git a/backend-java/src/main/java/com/tasteby/service/MemoService.java b/backend-java/src/main/java/com/tasteby/service/MemoService.java
index cd1dc79..1bb1c43 100644
--- a/backend-java/src/main/java/com/tasteby/service/MemoService.java
+++ b/backend-java/src/main/java/com/tasteby/service/MemoService.java
@@ -3,6 +3,7 @@ package com.tasteby.service;
 import com.tasteby.domain.Memo;
 import com.tasteby.mapper.MemoMapper;
 import com.tasteby.util.IdGenerator;
+import org.springframework.dao.DuplicateKeyException;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -25,11 +26,18 @@ public class MemoService {
     @Transactional
     public Memo upsert(String userId, String restaurantId, Double rating, String memoText, LocalDate visitedAt) {
         String visitedStr = visitedAt != null ? visitedAt.toString() : null;
+        // #294 — 동시성 가드: 사전 SELECT → 분기 INSERT/UPDATE 패턴은 두 트랜잭션이 동시에 미존재
+        // 판정 후 둘 다 INSERT → UNIQUE 충돌(500). INSERT 우선 시도 후 DuplicateKeyException 시 UPDATE.
         Memo existing = mapper.findByUserAndRestaurant(userId, restaurantId);
         if (existing != null) {
             mapper.updateMemo(userId, restaurantId, rating, memoText, visitedStr);
         } else {
-            mapper.insertMemo(IdGenerator.newId(), userId, restaurantId, rating, memoText, visitedStr);
+            try {
+                mapper.insertMemo(IdGenerator.newId(), userId, restaurantId, rating, memoText, visitedStr);
+            } catch (DuplicateKeyException e) {
+                // 동시 INSERT 충돌 → UPDATE로 폴백
+                mapper.updateMemo(userId, restaurantId, rating, memoText, visitedStr);
+            }
         }
         return mapper.findByUserAndRestaurant(userId, restaurantId);
     }
diff --git a/backend-java/src/main/java/com/tasteby/service/ReviewService.java b/backend-java/src/main/java/com/tasteby/service/ReviewService.java
index a95754b..ada2a90 100644
--- a/backend-java/src/main/java/com/tasteby/service/ReviewService.java
+++ b/backend-java/src/main/java/com/tasteby/service/ReviewService.java
@@ -5,6 +5,7 @@ import com.tasteby.domain.Review;
 import com.tasteby.mapper.ReviewMapper;
 import com.tasteby.util.IdGenerator;
 import com.tasteby.util.JsonUtil;
+import org.springframework.dao.DuplicateKeyException;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -60,10 +61,15 @@ public class ReviewService {
         if (existingId != null) {
             mapper.deleteFavorite(userId, restaurantId);
             return false;
-        } else {
-            mapper.insertFavorite(IdGenerator.newId(), userId, restaurantId);
-            return true;
         }
+        // #294 — 동시성 가드: 동시 INSERT 시 UNIQUE 충돌 → 한 쪽 500.
+        // INSERT 시도 후 DuplicateKeyException은 "이미 추가됨"으로 간주 (토글 의도는 ON).
+        try {
+            mapper.insertFavorite(IdGenerator.newId(), userId, restaurantId);
+        } catch (DuplicateKeyException ignored) {
+            // 다른 트랜잭션이 먼저 INSERT 함 — 결과는 어쨌든 즐겨찾기 ON.
+        }
+        return true;
     }
 
     public List<Restaurant> getUserFavorites(String userId) {
diff --git a/backend-java/src/main/resources/mybatis/mapper/ChannelMapper.xml b/backend-java/src/main/resources/mybatis/mapper/ChannelMapper.xml
index 6c669ca..ae65d4c 100644
--- a/backend-java/src/main/resources/mybatis/mapper/ChannelMapper.xml
+++ b/backend-java/src/main/resources/mybatis/mapper/ChannelMapper.xml
@@ -44,7 +44,8 @@
     </update>
 
     <select id="findByChannelId" resultMap="channelResultMap">
-        SELECT id, channel_id, channel_name, title_filter
+        <!-- #295 — findAllActive와 동일하게 description/tags/sort_order까지 SELECT -->
+        SELECT id, channel_id, channel_name, title_filter, description, tags, sort_order
         FROM channels
         WHERE channel_id = #{channelId} AND is_active = 1
     </select>
diff --git a/backend-java/src/main/resources/mybatis/mapper/ReviewMapper.xml b/backend-java/src/main/resources/mybatis/mapper/ReviewMapper.xml
index dcc0e7d..d055cbb 100644
--- a/backend-java/src/main/resources/mybatis/mapper/ReviewMapper.xml
+++ b/backend-java/src/main/resources/mybatis/mapper/ReviewMapper.xml
@@ -79,7 +79,8 @@
     </select>
 
     <select id="getAvgRating" resultType="map">
-        SELECT ROUND(AVG(rating), 1) AS avg_rating, COUNT(*) AS review_count
+        <!-- #294 — review 0건이면 AVG는 NULL → 클라이언트 NaN 처리 부담. NVL로 0.0 보장. -->
+        SELECT NVL(ROUND(AVG(rating), 1), 0) AS avg_rating, COUNT(*) AS review_count
         FROM user_reviews
         WHERE restaurant_id = #{restaurantId}
     </select>