diff --git a/src/main/java/LuckyVicky/backend/global/api_payload/ErrorCode.java b/src/main/java/LuckyVicky/backend/global/api_payload/ErrorCode.java
index 13114c5..67cf9a4 100644
--- a/src/main/java/LuckyVicky/backend/global/api_payload/ErrorCode.java
+++ b/src/main/java/LuckyVicky/backend/global/api_payload/ErrorCode.java
@@ -70,7 +70,8 @@ public enum ErrorCode implements BaseCode {
     PACHINKO_NO_MORE_CHANCE(HttpStatus.BAD_REQUEST, "PACHINKO_4002", "이미 세칸을 고르셨습니다."),
     PACHINKO_NO_REWARD(HttpStatus.NOT_FOUND, "PACHINKO_4042", "해당 보석 종류에 대한 보상 레코드가 없습니다."),
     PACHINKO_NO_PREVIOUS_ROUND(HttpStatus.NOT_FOUND, "PACHINKO_4043", "사용자가 빠칭코 게임을 한 전적이 없어 보상 반환이 불가합니다."),
-    PACHINKO_ALREADY_SELECT_SQUARE(HttpStatus.OK, "PACHINKO_4003", "해당 칸은 이미 다른 사용자에 의해 선택되었습니다."),
+    PACHINKO_ALREADY_SELECT_SQUARE(HttpStatus.BAD_REQUEST, "PACHINKO_4003", "해당 칸은 이미 다른 사용자에 의해 선택되었습니다."),
+    PACHINKO_NO_MORE_JEWEL(HttpStatus.BAD_REQUEST, "PACHINKO_4004", "이미 3칸을 선택하셔서 더 이상 칸을 선택할 수 없습니다."),
 
     // Ranking
     RANKING_WEEK_ITEM_LIST_EMPTY(HttpStatus.BAD_REQUEST, "RANKING_4001", "해당 주차에 강화한 상품이 없습니다."),
diff --git a/src/main/java/LuckyVicky/backend/pachinko/handler/PachinkoWebSocketHandler.java b/src/main/java/LuckyVicky/backend/pachinko/handler/PachinkoWebSocketHandler.java
index 81cdef8..aeca503 100644
--- a/src/main/java/LuckyVicky/backend/pachinko/handler/PachinkoWebSocketHandler.java
+++ b/src/main/java/LuckyVicky/backend/pachinko/handler/PachinkoWebSocketHandler.java
@@ -13,7 +13,6 @@
 import java.util.List;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
-import java.util.concurrent.Semaphore;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Component;
@@ -33,7 +32,6 @@ public class PachinkoWebSocketHandler extends TextWebSocketHandler {
     private final ObjectMapper objectMapper = new ObjectMapper();
     private final List<WebSocketSession> sessions = new ArrayList<>();
     private final ExecutorService virtualThreadExecutor = Executors.newVirtualThreadPerTaskExecutor();
-    private final Semaphore messageLimiter = new Semaphore(200); // 동시에 200개만 처리
 
     @Override
     public void afterConnectionEstablished(WebSocketSession session) {
@@ -100,10 +98,6 @@ private boolean validateJwt(WebSocketSession session, JsonNode node) throws IOEx
     }
 
     private boolean validateUserState(WebSocketSession session, User user, long currentRound) {
-        if (pachinkoService.noMoreJewel(user)) {
-            sendMessage(session, "칸을 선택할때 필요한 보석이 부족합니다.");
-            return false;
-        }
         if (!pachinkoService.canSelectMore(user, currentRound)) {
             sendMessage(session, "이미 " + PACHINKO_USER_MAX_SQUARES + "칸을 선택하셔서 더 이상 칸을 선택할 수 없습니다.");
             return false;
@@ -112,15 +106,14 @@ private boolean validateUserState(WebSocketSession session, User user, long curr
     }
 
     private void processSquareSelection(WebSocketSession session, User user, long currentRound, int selectedSquare) {
-        String result = pachinkoService.selectSquare(user, currentRound, selectedSquare);
+        String result = pachinkoService.selectSquare(user, selectedSquare);
         switch (result) {
             case "정상적으로 선택 완료되었습니다." -> {
                 broadcastMessage(user.getNickname() + "가 " + selectedSquare + "을 선택했습니다.");
                 checkGameStatusAndCloseSessionsIfNeeded();
             }
-            case "다른 사용자가 이전에 선택한 칸입니다." -> sendMessage(session, selectedSquare + "번째 칸은 이미 다른 사용자에 의해 선택되었습니다.");
-            case "본인이 이전에 선택한 칸입니다." -> sendMessage(session, selectedSquare + "번째 칸은 본인이 이전에 선택한 칸입니다.");
-            case null, default -> sendMessage(session, "이미 3칸을 선택하셔서 더 이상 칸을 선택할 수 없습니다.");
+            case "이미 선택된 칸입니다." -> sendMessage(session, selectedSquare + "번째 칸은 이미 다른 사용자에 의해 선택되었습니다.");
+            case "다른 사용자가 해당 칸을 선택 중입니다." -> sendMessage(session, selectedSquare + "번째 칸은 다른 사용자가 선택중인 칸입니다.");
         }
     }
 
diff --git a/src/main/java/LuckyVicky/backend/pachinko/repository/UserPachinkoRepository.java b/src/main/java/LuckyVicky/backend/pachinko/repository/UserPachinkoRepository.java
index b6dd497..682cbe0 100644
--- a/src/main/java/LuckyVicky/backend/pachinko/repository/UserPachinkoRepository.java
+++ b/src/main/java/LuckyVicky/backend/pachinko/repository/UserPachinkoRepository.java
@@ -15,7 +15,7 @@ public interface UserPachinkoRepository extends JpaRepository<UserPachinko, Long
 
     long countByUserAndRound(User user, Long round);
 
-    boolean existsByUserAndRoundAndSquare(User user, Long round, Integer square);
+    boolean existsByRoundAndSquare(Long round, Integer square);
 
     @Query("""
                 SELECT up FROM UserPachinko up
diff --git a/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoLoadTestWithVerification.java b/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoLoadTestWithVerification.java
index b0b1afe..2aafe1b 100644
--- a/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoLoadTestWithVerification.java
+++ b/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoLoadTestWithVerification.java
@@ -16,12 +16,11 @@
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
-import org.glassfish.tyrus.client.ClientManager;
 
 public class PachinkoLoadTestWithVerification {
 
-    private static final int USERS_PER_SQUARE = 1000;
-    private static final int TOTAL_SQUARES = 5;
+    private static final int USERS_PER_SQUARE = 30;
+    private static final int TOTAL_SQUARES = 36;
     private static final String TOKEN_URL = "http://localhost:8080/token/generate";
     private static final String WS_URL = "ws://localhost:8080/pachinko";
     private static final String VERIFY_URL = "http://localhost:8080/game/pachinko/selected-squares";
@@ -29,10 +28,7 @@ public class PachinkoLoadTestWithVerification {
     private static final ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor();
 
     public static void main(String[] args) throws Exception {
-        WebSocketContainer container = ClientManager.createClient();
-        //WebSocketContainer container = ContainerProvider.getWebSocketContainer();
-        System.out.println("사용 중인 WebSocketContainer 구현체: " + container.getClass().getName());
-
+        long start = System.nanoTime();
         CountDownLatch latch = new CountDownLatch(USERS_PER_SQUARE * TOTAL_SQUARES);
 
         for (int square = 1; square <= TOTAL_SQUARES; square++) {
@@ -56,13 +52,17 @@ public static void main(String[] args) throws Exception {
         executor.shutdown();
         System.out.println("make user finish");
 
+        long end = System.nanoTime();
+
         // 결과 검증
         Thread.sleep(2000); // 데이터 반영 대기
         verifySelectedSquares();
+
+        double elapsedMs = (end - start) / 1_000_000.0;
+        System.out.printf("부하 테스트 완료 – 총 소요 시간: %.2fms (%.2f초)\n", elapsedMs, elapsedMs / 1000.0);
     }
 
     private static String getTokenForUser(int userNum) throws Exception {
-        System.out.println(userNum);
         URL url = new URL(TOKEN_URL);
         HttpURLConnection con = (HttpURLConnection) url.openConnection();
         con.setRequestMethod("POST");
@@ -87,9 +87,7 @@ private static String getTokenForUser(int userNum) throws Exception {
                 String response = scanner.hasNext() ? scanner.next() : "";
                 ObjectMapper mapper = new ObjectMapper();
                 JsonNode root = mapper.readTree(response);
-                String token = root.get("result").get("accessToken").asText();
-                System.out.println(token);
-                return token;
+                return root.get("result").get("accessToken").asText();
 
             }
         } else {
@@ -127,9 +125,6 @@ private static void verifySelectedSquares() throws Exception {
         if (con.getResponseCode() == 200) {
             try (Scanner scanner = new Scanner(con.getInputStream()).useDelimiter("\\A")) {
                 String response = scanner.hasNext() ? scanner.next() : "";
-                System.out.println("선택된 칸 결과 확인 응답:");
-                System.out.println(response);
-
                 int resultStart = response.indexOf("[");
                 int resultEnd = response.indexOf("]", resultStart) + 1;
                 String resultJsonArray = response.substring(resultStart, resultEnd);
@@ -137,7 +132,7 @@ private static void verifySelectedSquares() throws Exception {
 
                 System.out.printf("최종 선택된 칸 개수: %d개%n", squares.length);
                 if (squares.length == TOTAL_SQUARES) {
-                    System.out.printf("테스트 성공: %d개 칸이 정확히 채워졌습니다.", squares.length);
+                    System.out.printf("테스트 성공: %d개 칸이 정확히 채워졌습니다.\n", squares.length);
                 } else {
                     System.err.println("테스트 실패: 선택된 칸 수 = " + squares.length);
                 }
diff --git a/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoService.java b/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoService.java
index b1c204d..e659ca5 100644
--- a/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoService.java
+++ b/src/main/java/LuckyVicky/backend/pachinko/service/PachinkoService.java
@@ -20,6 +20,7 @@
 import LuckyVicky.backend.user.domain.UserJewel;
 import LuckyVicky.backend.user.repository.UserJewelRepository;
 import LuckyVicky.backend.user.repository.UserRepository;
+import LuckyVicky.backend.user.service.UserJewelService;
 import jakarta.annotation.PostConstruct;
 import jakarta.transaction.Transactional;
 import java.security.SecureRandom;
@@ -31,13 +32,11 @@
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Collectors;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
-import org.springframework.dao.DataIntegrityViolationException;
-import org.springframework.retry.annotation.Backoff;
-import org.springframework.retry.annotation.Retryable;
 import org.springframework.stereotype.Service;
 
 @Slf4j
@@ -61,10 +60,12 @@ public class PachinkoService {
     private final UserJewelRepository userJewelRepository;
     private final UserRepository userRepository;
     private final DisplayBoardService displayBoardService;
+    private final UserJewelService userJewelService;
     private final FcmService fcmService;
 
     @Getter
-    private final Set<Integer> selectedSquares = ConcurrentHashMap.newKeySet();
+    private final Set<Integer> selectedSquares = ConcurrentHashMap.newKeySet(); // 캐시에 미리 선택되지 않았다는 데이터 넣어두자
+    private final ConcurrentHashMap<Integer, ReentrantLock> squareLocks = new ConcurrentHashMap<>();
 
     public Set<Integer> viewSelectedSquares() { // 읽기 전용 뷰 반환
         return Collections.unmodifiableSet(selectedSquares);
@@ -99,71 +100,54 @@ public void startNewRound() {
         assignRewardsToSquares(currentRound);
     }
 
-    @Transactional
-    public boolean noMoreJewel(User user) {
-        UserJewel userJewel = userJewelRepository.findByUserAndJewelType(user, PACHINKO_NEED_JEWEL_TYPE)
-                .orElseThrow(() -> new GeneralException(ErrorCode.USER_JEWEL_NOT_FOUND));
-
-        return userJewel.getCount() < PACHINKO_NEED_JEWEL_COUNT;
-    }
-
     @Transactional
     public boolean canSelectMore(User user, Long round) {
         return userPachinkoRepository.countByUserAndRound(user, round) < PACHINKO_USER_MAX_SQUARES;
     }
 
     @Transactional
-    @Retryable(
-            value = DataIntegrityViolationException.class,
-            maxAttempts = 2,
-            backoff = @Backoff(delay = 100, multiplier = 2)
-    )
-    public String selectSquare(User user, long currentRound, int squareNumber) {
+    public String selectSquare(User user, int squareNumber) {
         // 칸 번호 유효성 검증
         validateSquareNumber(squareNumber);
 
-        // 이미 선택된 칸인지 확인
+        // 캐시 검증
         if (selectedSquares.contains(squareNumber)) {
-            log.info("{} 이미 {}가 선택되었습니다.", selectedSquares, squareNumber);
-
-            boolean userAlreadySelected = userPachinkoRepository.existsByUserAndRoundAndSquare(user, currentRound,
-                    squareNumber);
+            return "이미 선택된 칸입니다.";
+        }
 
-            if (userAlreadySelected) {
-                log.info("본인이 이전에 선택한 칸입니다.");
-                return "본인이 이전에 선택한 칸입니다.";
-            } else {
-                log.info("다른 사용자가 이전에 선택한 칸입니다.");
-                return "다른 사용자가 이전에 선택한 칸입니다.";
-            }
+        // lock 획득 시도
+        ReentrantLock lock = squareLocks.computeIfAbsent(squareNumber, key -> new ReentrantLock());
+        if (!lock.tryLock()) {
+            return "다른 사용자가 해당 칸을 선택 중입니다.";
         }
+        try {
+            // DB, 캐시 갱신 이전 재확인
+            if (selectedSquares.contains(squareNumber)) {
+                return "이미 선택된 칸입니다.";
+            }
 
-        // 사용자 Pachinko 상태 저장
-        userPachinkoRepository.save(PachinkoConverter.saveUserPachinko(user, currentRound, squareNumber));
-        log.info("user pachinko에 선택한 칸인 {}을 저장했습니다.", squareNumber);
+            // 보석 개수 확인 후 차감
+            userJewelService.deductUserJewel(user);
+            log.info("빠칭코 칸 선택을 위해 B급 보석 하나를 지불하여 DB에서 보석을 차감했습니다.");
 
-        // 선택한 칸을 set에 추가
-        addSelectedSquare(squareNumber);
-        log.info("선택한 칸을 set에 삽입했습니다. 변경된 set: {}", selectedSquares);
+            // 캐시 갱신
+            addSelectedSquare(squareNumber);
+            log.info("선택한 칸을 set에 삽입했습니다. 변경된 set: {}", selectedSquares);
 
-        // 보석 차감
-        deductUserJewel(user);
-        log.info("빠칭코 칸 선택을 위해 B급 보석 하나를 지불하여 DB에서 보석을 차감했습니다.");
+            // DB 갱신
+            userPachinkoRepository.save(PachinkoConverter.saveUserPachinko(user, currentRound, squareNumber));
+            log.info("user pachinko에 선택한 칸인 {}을 저장했습니다.", squareNumber);
 
-        return "정상적으로 선택 완료되었습니다.";
+            return "정상적으로 선택 완료되었습니다.";
+        } finally {
+            lock.unlock();
+        }
     }
 
     public void addSelectedSquare(int square) {
         selectedSquares.add(square);
     }
 
-    private void deductUserJewel(User user) {
-        UserJewel userJewel = userJewelRepository.findByUserAndJewelType(user, PACHINKO_NEED_JEWEL_TYPE)
-                .orElseThrow(() -> new GeneralException(ErrorCode.USER_JEWEL_NOT_FOUND));
-        userJewel.decreaseCount(PACHINKO_NEED_JEWEL_COUNT);
-        userJewelRepository.save(userJewel);
-    }
-
     private void validateSquareNumber(int squareNumber) {
         if (squareNumber < PACHINKO_MIN_SQUARE_NUMBER || squareNumber > PACHINKO_TOTAL_SQUARE_COUNT) {
             throw new GeneralException(ErrorCode.PACHINKO_OUT_OF_BOUND);
diff --git a/src/main/java/LuckyVicky/backend/user/repository/UserJewelRepository.java b/src/main/java/LuckyVicky/backend/user/repository/UserJewelRepository.java
index 3e2a2da..d3d0a48 100644
--- a/src/main/java/LuckyVicky/backend/user/repository/UserJewelRepository.java
+++ b/src/main/java/LuckyVicky/backend/user/repository/UserJewelRepository.java
@@ -3,13 +3,16 @@
 import LuckyVicky.backend.enhance.domain.JewelType;
 import LuckyVicky.backend.user.domain.User;
 import LuckyVicky.backend.user.domain.UserJewel;
+import jakarta.persistence.LockModeType;
 import java.util.Optional;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Lock;
 import org.springframework.stereotype.Repository;
 
 @Repository
 public interface UserJewelRepository extends JpaRepository<UserJewel, Long> {
     UserJewel findFirstByUserAndJewelType(User user, JewelType jewelType);
 
+    @Lock(LockModeType.PESSIMISTIC_WRITE)
     Optional<UserJewel> findByUserAndJewelType(User user, JewelType jewelType);
 }
diff --git a/src/main/java/LuckyVicky/backend/user/service/UserJewelService.java b/src/main/java/LuckyVicky/backend/user/service/UserJewelService.java
new file mode 100644
index 0000000..4052d01
--- /dev/null
+++ b/src/main/java/LuckyVicky/backend/user/service/UserJewelService.java
@@ -0,0 +1,36 @@
+package LuckyVicky.backend.user.service;
+
+import LuckyVicky.backend.enhance.domain.JewelType;
+import LuckyVicky.backend.global.api_payload.ErrorCode;
+import LuckyVicky.backend.global.exception.GeneralException;
+import LuckyVicky.backend.user.domain.User;
+import LuckyVicky.backend.user.domain.UserJewel;
+import LuckyVicky.backend.user.repository.UserJewelRepository;
+import jakarta.transaction.Transactional;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+@RequiredArgsConstructor
+@Service
+@Slf4j
+public class UserJewelService {
+
+    public final UserJewelRepository userJewelRepository;
+    private static final JewelType PACHINKO_NEED_JEWEL_TYPE = JewelType.B;
+    private static final int PACHINKO_NEED_JEWEL_COUNT = 1;
+
+    @Transactional
+    public void deductUserJewel(User user) {
+        // DB에서 락 걸고 사용자 보석 정보 조회
+        UserJewel userJewel = userJewelRepository.findByUserAndJewelType(user, PACHINKO_NEED_JEWEL_TYPE)
+                .orElseThrow(() -> new GeneralException(ErrorCode.USER_JEWEL_NOT_FOUND));
+        // 선택을 위한 코색 개수가 있는지
+        if (userJewel.getCount() < PACHINKO_NEED_JEWEL_COUNT) {
+            throw new GeneralException(ErrorCode.PACHINKO_NO_MORE_JEWEL);
+        }
+        // 보석 수량 차감
+        userJewel.decreaseCount(PACHINKO_NEED_JEWEL_COUNT);
+        userJewelRepository.save(userJewel);
+    }
+}