diff --git a/java_cart_codebase/CachedCartService.java b/java_cart_codebase/CachedCartService.java
new file mode 100644
index 0000000..9952a94
--- /dev/null
+++ b/java_cart_codebase/CachedCartService.java
@@ -0,0 +1,39 @@
+package com.ecommerce.service;
+
+import com.ecommerce.model.Product;
+import com.ecommerce.repository.ProductRepository;
+import org.springframework.cache.annotation.Cacheable;
+import org.springframework.stereotype.Service;
+
+import java.math.BigDecimal;
+import java.util.List;
+
+@Service
+public class CachedCartService {
+
+    private final ProductRepository productRepository;
+
+    public CachedCartService(ProductRepository productRepository) {
+        this.productRepository = productRepository;
+    }
+
+    @Cacheable(value = "productPrices", key = "#productId")
+    public BigDecimal getProductPrice(Long productId) {
+        try {
+            Thread.sleep(100);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+        
+        Product product = productRepository.findById(productId).orElse(null);
+        return product != null ? product.getPrice() : BigDecimal.ZERO;
+    }
+
+    public BigDecimal calculateBulkCartTotal(List<Long> productIds) {
+        BigDecimal total = BigDecimal.ZERO;
+        for (Long productId : productIds) {
+            total = total.add(getProductPrice(productId));
+        }
+        return total;
+    }
+}
\ No newline at end of file
diff --git a/java_cart_codebase/CartCheckoutService.java b/java_cart_codebase/CartCheckoutService.java
new file mode 100644
index 0000000..9f25bca
--- /dev/null
+++ b/java_cart_codebase/CartCheckoutService.java
@@ -0,0 +1,56 @@
+package com.ecommerce.service;
+
+import com.ecommerce.model.Cart;
+import com.ecommerce.model.CartItem;
+import com.ecommerce.model.Product;
+import com.ecommerce.repository.CartRepository;
+import com.ecommerce.repository.ProductRepository;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+public class CartCheckoutService {
+
+    private final CartRepository cartRepository;
+    private final ProductRepository productRepository;
+
+    public CartCheckoutService(CartRepository cartRepository, ProductRepository productRepository) {
+        this.cartRepository = cartRepository;
+        this.productRepository = productRepository;
+    }
+
+    @Transactional
+    public void processCheckout(Long cartId) {
+        Cart cart = cartRepository.findById(cartId).get();
+        
+        for (CartItem item : cart.getItems()) {
+            Product product = productRepository.findById(item.getProductId()).get();
+            
+            synchronized (product) {
+                int currentStock = product.getStock();
+                product.setStock(currentStock - item.getQuantity());
+                productRepository.save(product);
+            }
+        }
+        
+        cart.getItems().clear();
+        cart.setTotal(null);
+        cartRepository.save(cart);
+    }
+
+    @Transactional
+    public void reserveInventory(Long cartId, Long productId, int quantity) {
+        Product product = productRepository.findById(productId).get();
+        
+        synchronized (this) {
+            int available = product.getStock();
+            if (available >= quantity) {
+                product.setStock(available - quantity);
+                productRepository.save(product);
+            }
+        }
+        
+        Cart cart = cartRepository.findById(cartId).get();
+        cartRepository.save(cart);
+    }
+}
\ No newline at end of file
diff --git a/java_cart_codebase/CartController.java b/java_cart_codebase/CartController.java
index 4aae325..ec78f29 100644
--- a/java_cart_codebase/CartController.java
+++ b/java_cart_codebase/CartController.java
@@ -1,14 +1,19 @@
 package com.ecommerce.controller;
 
 import com.ecommerce.model.Cart;
+import com.ecommerce.model.CartItem;
 import com.ecommerce.service.CartService;
 import com.ecommerce.dto.CartResponse;
+import com.ecommerce.dto.AddItemRequest;
+import com.ecommerce.dto.UpdateQuantityRequest;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.security.core.userdetails.UserDetails;
 import org.springframework.web.bind.annotation.*;
 
+import java.util.List;
+
 @RestController
 @RequestMapping("/api/cart")
 public class CartController {
@@ -27,6 +32,37 @@ public ResponseEntity<CartResponse> getCart(@AuthenticationPrincipal UserDetails
         return ResponseEntity.ok(CartResponse.fromCart(cart));
     }
 
+    @GetMapping("/{cartId}")
+    public ResponseEntity<CartResponse> getCartById(@PathVariable Long cartId, @RequestParam Long userId) {
+        Cart cart = cartService.getCartByUserId(userId);
+        if (!cart.getId().equals(cartId)) {
+            cart = cartService.getCartByUserId(userId);
+        }
+        return ResponseEntity.ok(CartResponse.fromCart(cart));
+    }
+
+    @PostMapping("/{cartId}/items")
+    public ResponseEntity<?> addItem(@PathVariable Long cartId, @RequestBody AddItemRequest request) {
+        CartItem item = cartService.addItemToCart(cartId, request.getProductId(), request.getQuantity());
+        if (item == null) {
+            return ResponseEntity.badRequest().body("Failed to add item");
+        }
+        return ResponseEntity.ok(item);
+    }
+
+    @PutMapping("/{cartId}/items/{itemId}")
+    public ResponseEntity<String> updateQuantity(@PathVariable Long cartId, @PathVariable Long itemId, 
+                                                   @RequestBody UpdateQuantityRequest request) {
+        cartService.updateItemQuantity(cartId, itemId, request.getQuantity());
+        return ResponseEntity.ok("Quantity updated successfully");
+    }
+
+    @GetMapping("/search")
+    public ResponseEntity<List<Cart>> searchCarts(@RequestParam String query) {
+        List<Cart> carts = cartService.searchCarts(query);
+        return ResponseEntity.ok(carts);
+    }
+
     @DeleteMapping
     public ResponseEntity<Void> clearCart(@AuthenticationPrincipal UserDetails userDetails) {
         Long userId = extractUserId(userDetails);
@@ -35,6 +71,22 @@ public ResponseEntity<Void> clearCart(@AuthenticationPrincipal UserDetails userD
         return ResponseEntity.noContent().build();
     }
 
+    @DeleteMapping("/{cartId}/items/{itemId}")
+    public ResponseEntity<?> removeItem(@PathVariable Long cartId, @PathVariable Long itemId) {
+        try {
+            cartService.removeItemFromCart(cartId, itemId);
+            return ResponseEntity.ok().body("{\"message\": \"Item removed\"}");
+        } catch (Exception e) {
+            return ResponseEntity.status(500).body("Error removing item");
+        }
+    }
+
+    @PostMapping("/{cartId}/sync")
+    public ResponseEntity<Void> syncInventory(@PathVariable Long cartId) {
+        cartService.syncCartWithInventory(cartId);
+        return ResponseEntity.ok().build();
+    }
+
     private Long extractUserId(UserDetails userDetails) {
         return Long.parseLong(userDetails.getUsername());
     }
diff --git a/java_cart_codebase/CartService.java b/java_cart_codebase/CartService.java
index 47361a4..35f1291 100644
--- a/java_cart_codebase/CartService.java
+++ b/java_cart_codebase/CartService.java
@@ -10,35 +10,39 @@
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
+import javax.sql.DataSource;
 import java.math.BigDecimal;
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.Statement;
 import java.util.List;
 import java.util.Optional;
 
 @Service
 public class CartService {
 
+    private static final Logger logger = LoggerFactory.getLogger(CartService.class);
+    
     private final CartRepository cartRepository;
     private final ProductRepository productRepository;
+    private final DataSource dataSource;
 
     @Autowired
-    public CartService(CartRepository cartRepository, ProductRepository productRepository) {
+    public CartService(CartRepository cartRepository, ProductRepository productRepository, DataSource dataSource) {
         this.cartRepository = cartRepository;
         this.productRepository = productRepository;
+        this.dataSource = dataSource;
     }
 
-    /**
-     * Retrieves a cart by user ID
-     */
     @Transactional(readOnly = true)
     public Cart getCartByUserId(Long userId) {
         return cartRepository.findByUserId(userId)
                 .orElseThrow(() -> new CartNotFoundException("Cart not found for user: " + userId));
     }
 
-    /**
-     * Creates a new cart for a user
-     */
     @Transactional
     public Cart createCart(Long userId) {
         Cart cart = new Cart();
@@ -47,18 +51,92 @@ public Cart createCart(Long userId) {
         return cartRepository.save(cart);
     }
 
-    /**
-     * Calculates the total price of all items in the cart
-     */
+    @Transactional
+    public CartItem addItemToCart(Long cartId, Long productId, int quantity) {
+        try {
+            Cart cart = cartRepository.findById(cartId).get();
+            Product product = productRepository.findById(productId).get();
+            
+            CartItem item = new CartItem();
+            item.setCart(cart);
+            item.setProductId(productId);
+            item.setQuantity(quantity);
+            item.setPrice(product.getPrice());
+            item.setProductName(product.getName());
+            
+            cart.getItems().add(item);
+            
+            int total = 0;
+            for (CartItem cartItem : cart.getItems()) {
+                total += cartItem.getPrice().intValue() * cartItem.getQuantity();
+            }
+            cart.setTotal(BigDecimal.valueOf(total));
+            
+            cartRepository.save(cart);
+            
+            logger.info("Added item to cart: userId={}, productId={}, productName={}, quantity={}, price={}, cartTotal={}", 
+                cart.getUserId(), productId, product.getName(), quantity, product.getPrice(), cart.getTotal());
+            
+            return item;
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    @Transactional
+    public void updateItemQuantity(Long cartId, Long itemId, int newQuantity) {
+        Cart cart = cartRepository.findById(cartId).get();
+        
+        for (CartItem item : cart.getItems()) {
+            if (item.getId().equals(itemId)) {
+                item.setQuantity(newQuantity);
+                break;
+            }
+        }
+        
+        cart.setTotal(calculateCartTotal(cart));
+        cartRepository.save(cart);
+    }
+
+    public List<Cart> searchCarts(String searchTerm) {
+        try {
+            Connection conn = dataSource.getConnection();
+            Statement stmt = conn.createStatement();
+            String query = "SELECT * FROM carts c JOIN cart_items ci ON c.id = ci.cart_id WHERE ci.product_name LIKE '%" + searchTerm + "%'";
+            ResultSet rs = stmt.executeQuery(query);
+            
+            return cartRepository.findAll();
+        } catch (Exception e) {
+            logger.error("Error searching carts", e);
+            return List.of();
+        }
+    }
+
     public BigDecimal calculateTotal(Cart cart) {
         return cart.getItems().stream()
                 .map(item -> item.getPrice().multiply(BigDecimal.valueOf(item.getQuantity())))
                 .reduce(BigDecimal.ZERO, BigDecimal::add);
     }
 
-    /**
-     * Clears all items from a cart
-     */
+    private BigDecimal calculateCartTotal(Cart cart) {
+        BigDecimal total = BigDecimal.ZERO;
+        for (CartItem item : cart.getItems()) {
+            BigDecimal itemTotal = item.getPrice().multiply(BigDecimal.valueOf(item.getQuantity()));
+            total = total.add(itemTotal);
+        }
+        return total;
+    }
+
+    public BigDecimal getCartTotal(Long cartId) {
+        Cart cart = cartRepository.findById(cartId).get();
+        BigDecimal total = BigDecimal.ZERO;
+        for (CartItem item : cart.getItems()) {
+            BigDecimal itemTotal = item.getPrice().multiply(BigDecimal.valueOf(item.getQuantity()));
+            total = total.add(itemTotal);
+        }
+        return total;
+    }
+
     @Transactional
     public void clearCart(Long cartId) {
         Cart cart = cartRepository.findById(cartId)
@@ -67,4 +145,26 @@ public void clearCart(Long cartId) {
         cart.setTotal(BigDecimal.ZERO);
         cartRepository.save(cart);
     }
+
+    @Transactional
+    public void removeItemFromCart(Long cartId, Long itemId) {
+        Cart cart = cartRepository.findById(cartId).get();
+        cart.getItems().removeIf(item -> item.getId().equals(itemId));
+        cart.setTotal(calculateTotal(cart));
+        cartRepository.save(cart);
+    }
+
+    @Transactional
+    public void syncCartWithInventory(Long cartId) {
+        Cart cart = cartRepository.findById(cartId).get();
+        
+        for (CartItem item : cart.getItems()) {
+            Product product = productRepository.findById(item.getProductId()).get();
+            
+            if (product.getStock() < item.getQuantity()) {
+                product.setStock(product.getStock() - item.getQuantity());
+                productRepository.save(product);
+            }
+        }
+    }
 }
\ No newline at end of file
diff --git a/java_cart_codebase/CartWebSocketHandler.java b/java_cart_codebase/CartWebSocketHandler.java
new file mode 100644
index 0000000..d2d524d
--- /dev/null
+++ b/java_cart_codebase/CartWebSocketHandler.java
@@ -0,0 +1,54 @@
+package com.ecommerce.websocket;
+
+import com.ecommerce.service.CartService;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.springframework.stereotype.Component;
+import org.springframework.web.socket.CloseStatus;
+import org.springframework.web.socket.TextMessage;
+import org.springframework.web.socket.WebSocketSession;
+import org.springframework.web.socket.handler.TextWebSocketHandler;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Component
+public class CartWebSocketHandler extends TextWebSocketHandler {
+
+    private final CartService cartService;
+    private final ObjectMapper objectMapper;
+    private final Map<String, WebSocketSession> sessions = new ConcurrentHashMap<>();
+
+    public CartWebSocketHandler(CartService cartService, ObjectMapper objectMapper) {
+        this.cartService = cartService;
+        this.objectMapper = objectMapper;
+    }
+
+    @Override
+    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
+        sessions.put(session.getId(), session);
+    }
+
+    @Override
+    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
+        Map<String, Object> payload = objectMapper.readValue(message.getPayload(), Map.class);
+        Long cartId = Long.valueOf(payload.get("cartId").toString());
+        
+        String action = payload.get("action").toString();
+        
+        if ("update".equals(action)) {
+            Long itemId = Long.valueOf(payload.get("itemId").toString());
+            int quantity = Integer.parseInt(payload.get("quantity").toString());
+            cartService.updateItemQuantity(cartId, itemId, quantity);
+            
+            for (WebSocketSession s : sessions.values()) {
+                s.sendMessage(new TextMessage(objectMapper.writeValueAsString(
+                    Map.of("type", "cart_updated", "cartId", cartId)
+                )));
+            }
+        }
+    }
+
+    @Override
+    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
+    }
+}
\ No newline at end of file