diff --git a/chapter-04/src/main/java/expert/os/books/ddd/chapter04/Customer.java b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/Customer.java
new file mode 100644
index 0000000..71df626
--- /dev/null
+++ b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/Customer.java
@@ -0,0 +1,5 @@
+package expert.os.books.ddd.chapter04;
+
+public record Customer(String name, String email) {
+
+}
diff --git a/chapter-04/src/main/java/expert/os/books/ddd/chapter04/CustomerCategory.java b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/CustomerCategory.java
new file mode 100644
index 0000000..587cd3a
--- /dev/null
+++ b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/CustomerCategory.java
@@ -0,0 +1,38 @@
+package expert.os.books.ddd.chapter04;
+
+public enum CustomerCategory {
+
+    BRONZE(0, 0),
+    SILVER(1000, 5),
+    GOLD(5000, 10),
+    PLATINUM(10000, 15);
+
+    private final int pointsThreshold;
+    private final int discountPercentage;
+
+    CustomerCategory(int pointsThreshold, int discountPercentage) {
+        this.pointsThreshold = pointsThreshold;
+        this.discountPercentage = discountPercentage;
+    }
+
+    public int pointsThreshold() {
+        return pointsThreshold;
+    }
+
+    public int discountPercentage() {
+        return discountPercentage;
+    }
+
+    public static CustomerCategory getCategoryByPoints(int points) {
+        if (points >= PLATINUM.pointsThreshold) {
+            return PLATINUM;
+        } else if (points >= GOLD.pointsThreshold) {
+            return GOLD;
+        } else if (points >= SILVER.pointsThreshold) {
+            return SILVER;
+        } else {
+            return BRONZE;
+        }
+    }
+
+}
diff --git a/chapter-04/src/main/java/expert/os/books/ddd/chapter04/LoyaltyCard.java b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/LoyaltyCard.java
new file mode 100644
index 0000000..3f6e6b2
--- /dev/null
+++ b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/LoyaltyCard.java
@@ -0,0 +1,51 @@
+package expert.os.books.ddd.chapter04;
+
+public class LoyaltyCard {
+
+    private final String id;
+
+    private final Customer customer;
+    private LoyaltyPoints loyaltyPoints;
+    private boolean isPremium;
+    private CustomerCategory category;
+
+    public LoyaltyCard(String id, Customer customer) {
+        this.id = id;
+        this.customer = customer;
+        this.loyaltyPoints = new LoyaltyPoints(0);
+        this.isPremium = false;
+        this.category = CustomerCategory.BRONZE;
+    }
+
+    public String getId() {
+        return id;
+    }
+
+    public Customer getCustomer() {
+        return customer;
+    }
+
+    public int getPoints() {
+        return loyaltyPoints.getPoints();
+    }
+
+    public boolean isPremium() {
+        return isPremium;
+    }
+
+    public CustomerCategory getCategory() {
+        return category;
+    }
+
+    public void addPoints(int points) {
+        loyaltyPoints.addPoints(points);
+        updateCategory();
+        if (loyaltyPoints.canUpgradeToPremium()) {
+            this.isPremium = true;
+        }
+    }
+
+    private void updateCategory() {
+        this.category = CustomerCategory.getCategoryByPoints(loyaltyPoints.getPoints());
+    }
+}
diff --git a/chapter-04/src/main/java/expert/os/books/ddd/chapter04/LoyaltyPoints.java b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/LoyaltyPoints.java
new file mode 100644
index 0000000..ae37251
--- /dev/null
+++ b/chapter-04/src/main/java/expert/os/books/ddd/chapter04/LoyaltyPoints.java
@@ -0,0 +1,22 @@
+package expert.os.books.ddd.chapter04;
+
+public class LoyaltyPoints {
+
+    private int points;
+
+    public LoyaltyPoints(int initialPoints) {
+        this.points = initialPoints;
+    }
+
+    public int getPoints() {
+        return points;
+    }
+
+    public void addPoints(int additionalPoints) {
+        this.points += additionalPoints;
+    }
+
+    public boolean canUpgradeToPremium() {
+        return this.points >= 1000;
+    }
+}