diff --git a/backend/src/main/java/com/openisle/controller/CategoryController.java b/backend/src/main/java/com/openisle/controller/CategoryController.java
index 4df6f20af..37282bc39 100644
--- a/backend/src/main/java/com/openisle/controller/CategoryController.java
+++ b/backend/src/main/java/com/openisle/controller/CategoryController.java
@@ -12,6 +12,7 @@ import lombok.RequiredArgsConstructor;
 import org.springframework.web.bind.annotation.*;
 
 import java.util.List;
+import java.util.Map;
 import java.util.stream.Collectors;
 
 @RestController
@@ -44,8 +45,11 @@ public class CategoryController {
 
     @GetMapping
     public List<CategoryDto> list() {
-        return categoryService.listCategories().stream()
-                .map(c -> categoryMapper.toDto(c, postService.countPostsByCategory(c.getId())))
+        List<Category> all = categoryService.listCategories();
+        List<Long> ids = all.stream().map(Category::getId).toList();
+        Map<Long, Long> postsCntByCategoryIds = postService.countPostsByCategoryIds(ids);
+        return all.stream()
+                .map(c -> categoryMapper.toDto(c, postsCntByCategoryIds.getOrDefault(c.getId(), 0L)))
                 .sorted((a, b) -> Long.compare(b.getCount(), a.getCount()))
                 .collect(Collectors.toList());
     }
diff --git a/backend/src/main/java/com/openisle/controller/TagController.java b/backend/src/main/java/com/openisle/controller/TagController.java
index 72db5eda5..3c7df2421 100644
--- a/backend/src/main/java/com/openisle/controller/TagController.java
+++ b/backend/src/main/java/com/openisle/controller/TagController.java
@@ -15,6 +15,7 @@ import lombok.RequiredArgsConstructor;
 import org.springframework.web.bind.annotation.*;
 
 import java.util.List;
+import java.util.Map;
 import java.util.stream.Collectors;
 
 @RestController
@@ -62,8 +63,11 @@ public class TagController {
     @GetMapping
     public List<TagDto> list(@RequestParam(value = "keyword", required = false) String keyword,
                              @RequestParam(value = "limit", required = false) Integer limit) {
-        List<TagDto> dtos = tagService.searchTags(keyword).stream()
-                .map(t -> tagMapper.toDto(t, postService.countPostsByTag(t.getId())))
+        List<Tag> tags = tagService.searchTags(keyword);
+        List<Long> tagIds = tags.stream().map(Tag::getId).toList();
+        Map<Long, Long> postCntByTagIds = postService.countPostsByTagIds(tagIds);
+        List<TagDto> dtos = tags.stream()
+                .map(t -> tagMapper.toDto(t, postCntByTagIds.getOrDefault(t.getId(), 0L)))
                 .sorted((a, b) -> Long.compare(b.getCount(), a.getCount()))
                 .collect(Collectors.toList());
         if (limit != null && limit > 0 && dtos.size() > limit) {
diff --git a/backend/src/main/java/com/openisle/repository/PostRepository.java b/backend/src/main/java/com/openisle/repository/PostRepository.java
index df0905792..d764bb1dd 100644
--- a/backend/src/main/java/com/openisle/repository/PostRepository.java
+++ b/backend/src/main/java/com/openisle/repository/PostRepository.java
@@ -92,8 +92,14 @@ public interface PostRepository extends JpaRepository<Post, Long> {
 
     long countByCategory_Id(Long categoryId);
 
+    @Query("SELECT c.id, COUNT(p) FROM Post p JOIN p.category c WHERE c.id IN :categoryIds GROUP BY c.id")
+    List<Object[]> countPostsByCategoryIds(@Param("categoryIds") List<Long> categoryIds);
+
     long countDistinctByTags_Id(Long tagId);
 
+    @Query("SELECT t.id, COUNT(DISTINCT p) FROM Post p JOIN p.tags t WHERE t.id IN :tagIds GROUP BY t.id")
+    List<Object[]> countPostsByTagIds(@Param("tagIds") List<Long> tagIds);
+
     long countByAuthor_Id(Long userId);
 
     @Query("SELECT FUNCTION('date', p.createdAt) AS d, COUNT(p) AS c FROM Post p " +
diff --git a/backend/src/main/java/com/openisle/service/PostService.java b/backend/src/main/java/com/openisle/service/PostService.java
index 7b2558e43..30a785ce5 100644
--- a/backend/src/main/java/com/openisle/service/PostService.java
+++ b/backend/src/main/java/com/openisle/service/PostService.java
@@ -31,16 +31,15 @@ import com.openisle.service.EmailSender;
 
 import java.time.ZoneId;
 import java.time.ZoneOffset;
-import java.util.List;
+import java.util.*;
+
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.util.CollectionUtils;
 
 import java.time.LocalDateTime;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashSet;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.ScheduledFuture;
@@ -567,10 +566,31 @@ public class PostService {
         return postRepository.countByCategory_Id(categoryId);
     }
 
+    public Map<Long, Long> countPostsByCategoryIds(List<Long> categoryIds) {
+        Map<Long, Long> result = new HashMap<>();
+        var dbResult = postRepository.countPostsByCategoryIds(categoryIds);
+        dbResult.forEach(r -> {
+            result.put(((Long)r[0]), ((Long)r[1]));
+        });
+        return result;
+    }
+
     public long countPostsByTag(Long tagId) {
         return postRepository.countDistinctByTags_Id(tagId);
     }
 
+    public Map<Long, Long> countPostsByTagIds(List<Long> tagIds) {
+        Map<Long, Long> result = new HashMap<>();
+        if (CollectionUtils.isEmpty(tagIds)) {
+            return result;
+        }
+        var dbResult = postRepository.countPostsByTagIds(tagIds);
+        dbResult.forEach(r -> {
+            result.put(((Long)r[0]), ((Long)r[1]));
+        });
+        return result;
+    }
+
     private java.util.List<Post> sortByPinnedAndCreated(java.util.List<Post> posts) {
         return posts.stream()
                 .sorted(java.util.Comparator