diff --git a/src/main/java/mate/academy/bookstore/dto/ShoppingCartRequestDto.java b/src/main/java/mate/academy/bookstore/dto/ShoppingCartRequestDto.java
index a49f07c..d6874c3 100644
--- a/src/main/java/mate/academy/bookstore/dto/ShoppingCartRequestDto.java
+++ b/src/main/java/mate/academy/bookstore/dto/ShoppingCartRequestDto.java
@@ -1,5 +1,6 @@
 package mate.academy.bookstore.dto;
 
+import jakarta.validation.Valid;
 import jakarta.validation.constraints.NotEmpty;
 import java.util.Set;
 import lombok.Data;
@@ -7,5 +8,6 @@
 @Data
 public class ShoppingCartRequestDto {
     @NotEmpty
+    @Valid
     private Set<CartItemRequestDto> cartItems;
 }
diff --git a/src/main/java/mate/academy/bookstore/model/CartItem.java b/src/main/java/mate/academy/bookstore/model/CartItem.java
index d0c4854..bdc67f8 100644
--- a/src/main/java/mate/academy/bookstore/model/CartItem.java
+++ b/src/main/java/mate/academy/bookstore/model/CartItem.java
@@ -20,5 +20,6 @@ public class CartItem {
     private CartItemKey id;
 
     @Column(nullable = false)
+    @EqualsAndHashCode.Exclude
     private int quantity;
 }
diff --git a/src/main/java/mate/academy/bookstore/repository/CartItemRepository.java b/src/main/java/mate/academy/bookstore/repository/CartItemRepository.java
index 995adbc..f2fc7c9 100644
--- a/src/main/java/mate/academy/bookstore/repository/CartItemRepository.java
+++ b/src/main/java/mate/academy/bookstore/repository/CartItemRepository.java
@@ -4,5 +4,9 @@
 import mate.academy.bookstore.model.CartItemKey;
 import org.springframework.data.jpa.repository.JpaRepository;
 
+import java.util.List;
+import java.util.Set;
+
 public interface CartItemRepository extends JpaRepository<CartItem, CartItemKey> {
+    Set<CartItem> getById_Book_IdIn(List<Long> ids);
 }
diff --git a/src/main/java/mate/academy/bookstore/service/BookService.java b/src/main/java/mate/academy/bookstore/service/BookService.java
index e94af02..0f71eb6 100644
--- a/src/main/java/mate/academy/bookstore/service/BookService.java
+++ b/src/main/java/mate/academy/bookstore/service/BookService.java
@@ -18,4 +18,6 @@ public interface BookService {
     BookDto updateById(Long id, BookRequestDto bookRequestDto);
 
     void deleteById(Long id);
+
+    void validateBooksExistence(List<Long> booksIds);
 }
diff --git a/src/main/java/mate/academy/bookstore/service/impl/BookServiceImpl.java b/src/main/java/mate/academy/bookstore/service/impl/BookServiceImpl.java
index 9b7b0cb..9c24a98 100644
--- a/src/main/java/mate/academy/bookstore/service/impl/BookServiceImpl.java
+++ b/src/main/java/mate/academy/bookstore/service/impl/BookServiceImpl.java
@@ -90,6 +90,21 @@ public void deleteById(Long id) {
         bookRepository.deleteById(id);
     }
 
+    public void validateBooksExistence(List<Long> booksIds) {
+        Set<Long> existingBooks = bookRepository.findByIdIn(booksIds)
+                .stream()
+                .map(Book::getId)
+                .collect(Collectors.toSet());
+
+        if (existingBooks.size() != booksIds.size()) {
+            Set<Long> notFoundBooks = new HashSet<>(booksIds);
+            notFoundBooks.removeAll(existingBooks);
+            throw new EntityNotFoundException(
+                    localeService.getMessage("exception.notfound.books") + notFoundBooks
+            );
+        }
+    }
+
     private Book getBookByIdOrThrowException(Long id) {
         return bookRepository.findById(id)
                 .orElseThrow(() -> new EntityNotFoundException(
diff --git a/src/main/java/mate/academy/bookstore/service/impl/ShoppingCartServiceImpl.java b/src/main/java/mate/academy/bookstore/service/impl/ShoppingCartServiceImpl.java
index e1358bd..dc9c560 100644
--- a/src/main/java/mate/academy/bookstore/service/impl/ShoppingCartServiceImpl.java
+++ b/src/main/java/mate/academy/bookstore/service/impl/ShoppingCartServiceImpl.java
@@ -1,36 +1,34 @@
 package mate.academy.bookstore.service.impl;
 
-import jakarta.persistence.EntityManager;
-import jakarta.persistence.PersistenceContext;
+import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 import lombok.RequiredArgsConstructor;
+import mate.academy.bookstore.dto.CartItemRequestDto;
 import mate.academy.bookstore.dto.ShoppingCartDto;
 import mate.academy.bookstore.dto.ShoppingCartRequestDto;
 import mate.academy.bookstore.exception.EntityNotFoundException;
 import mate.academy.bookstore.mapper.ShoppingCartMapper;
 import mate.academy.bookstore.model.Book;
+import mate.academy.bookstore.model.CartItem;
 import mate.academy.bookstore.model.CartItemKey;
 import mate.academy.bookstore.model.ShoppingCart;
 import mate.academy.bookstore.model.User;
-import mate.academy.bookstore.repository.BookRepository;
 import mate.academy.bookstore.repository.CartItemRepository;
 import mate.academy.bookstore.repository.ShoppingCartRepository;
+import mate.academy.bookstore.service.BookService;
 import mate.academy.bookstore.service.LocaleService;
 import mate.academy.bookstore.service.ShoppingCartService;
 import org.springframework.stereotype.Service;
-import org.springframework.transaction.annotation.Transactional;
 
 @Service
 @RequiredArgsConstructor
 public class ShoppingCartServiceImpl implements ShoppingCartService {
     private final ShoppingCartRepository shoppingCartRepository;
     private final CartItemRepository cartItemRepository;
-    private final BookRepository bookRepository;
     private final ShoppingCartMapper shoppingCartMapper;
     private final LocaleService localeService;
-
-    @PersistenceContext
-    private EntityManager entityManager;
+    private final BookService bookService;
 
     @Override
     public void createFor(User user) {
@@ -41,8 +39,12 @@ public void createFor(User user) {
     }
 
     @Override
-    @Transactional
     public ShoppingCartDto save(ShoppingCartRequestDto dto, User user) {
+        List<Long> newBookIds = dto.getCartItems().stream()
+                .map(CartItemRequestDto::getBookId)
+                .toList();
+        bookService.validateBooksExistence(newBookIds);
+
         ShoppingCart shoppingCart = shoppingCartMapper.toModel(dto);
         shoppingCart.setUser(user);
         shoppingCart.setId(user.getId());
@@ -52,8 +54,10 @@ public ShoppingCartDto save(ShoppingCartRequestDto dto, User user) {
                 .collect(Collectors.toSet())
         );
 
-        ShoppingCart savedShoppingCart = shoppingCartRepository.saveAndFlush(shoppingCart);
-        entityManager.refresh(savedShoppingCart);
+        ShoppingCart savedShoppingCart = shoppingCartRepository.save(shoppingCart);
+        Set<CartItem> savedCartItems = cartItemRepository.getById_Book_IdIn(newBookIds);
+        savedShoppingCart.setCartItems(savedCartItems);
+
         return shoppingCartMapper.toDto(savedShoppingCart);
     }