Add daily rotating recommended category endpoint

src/main/java/com/ongil/backend/domain/category/controller/CategoryController.java

@@ -60,4 +60,13 @@ public DataResponse<List<CategorySimpleResponse>> getRecommendedSubCategories(
 		List<CategorySimpleResponse> categories = categoryService.getRecommendedSubCategories(count);
 		return DataResponse.from(categories);
 	}
+
+	@Operation(summary = "오늘의 추천 카테고리 조회", description = "오늘의 추천 카테고리를 조회합니다. 매일 다른 카테고리가 추천됩니다.")
+	@GetMapping("/today-recommended")
+	public DataResponse<List<CategorySimpleResponse>> getTodayRecommendedCategories(
+		@RequestParam(defaultValue = "8") @Min(1) @Max(100) int count
+	) {
+		List<CategorySimpleResponse> categories = categoryService.getTodayRecommendedCategories(count);
+		return DataResponse.from(categories);
+	}
 }

src/main/java/com/ongil/backend/domain/category/service/CategoryService.java

@@ -1,8 +1,10 @@
 package com.ongil.backend.domain.category.service;
 
+import java.time.LocalDate;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Random;
 import java.util.stream.Collectors;
 
 import org.springframework.stereotype.Service;
@@ -90,6 +92,47 @@ public List<CategorySimpleResponse> getRecommendedSubCategories(int count) {
 			.collect(Collectors.toList());
 	}
 
+	// 오늘의 추천 카테고리 조회 (매일 다른 카테고리)
+	public List<CategorySimpleResponse> getTodayRecommendedCategories(int count) {
+		LocalDate today = LocalDate.now();
+		// Redis 캐시 키에 날짜 포함
+		String cacheKey = CacheKeyConstants.TODAY_RECOMMENDED_CATEGORIES + ":" + today;
+
+		// Redis 캐시 확인
+		List<CategorySimpleResponse> cached = redisCacheService.getList(
+			cacheKey,
+			CategorySimpleResponse.class
+		);
+
+		if (cached != null && cached.size() >= count) {
+			return cached.stream()
+				.limit(count)
+				.collect(Collectors.toList());
+		}
+
+		// Cache Miss → DB 조회 후 날짜 기반 셔플
+		List<Category> subCategories = categoryRepository.findAllSubCategories();
+
+		// 날짜를 시드로 사용하여 매일 다른 순서로 셔플
+		List<Category> shuffledCategories = new ArrayList<>(subCategories);
+		long seed = today.toEpochDay(); // 날짜를 시드로 사용
+		Collections.shuffle(shuffledCategories, new Random(seed));
+
+		List<CategorySimpleResponse> response = shuffledCategories.stream()
+			.limit(count)
+			.map(categoryConverter::toSimpleResponse)
+			.collect(Collectors.toList());
+
+		// Redis 캐싱 (하루 동안 유지)
+		redisCacheService.save(
+			cacheKey,
+			response,
+			CacheKeyConstants.DAILY_TTL_HOURS
+		);
+
+		return response;
+	}
+
 	private String getTopProductThumbnail(Category category) {
 		Long targetCategoryId;
 

src/main/java/com/ongil/backend/global/config/redis/CacheKeyConstants.java

@@ -5,7 +5,9 @@ public class CacheKeyConstants {
 	// Brand/Category 캐시 관련
 	public static final String BRANDS_ALL = "BRANDS:ALL";
 	public static final String CATEGORIES_ALL = "CATEGORIES:ALL";
+	public static final String TODAY_RECOMMENDED_CATEGORIES = "CATEGORIES:TODAY_RECOMMENDED";
 	public static final long MASTER_DATA_TTL_HOURS = 0;  // 무한 TTL
+	public static final long DAILY_TTL_HOURS = 24;  // 하루 TTL
 
 	private CacheKeyConstants() {
 		throw new IllegalStateException("Utility class");