diff --git a/src/main/java/com/example/productaffinity/domain/port/incomming/GetAffinityProductsUC.java b/src/main/java/com/example/productaffinity/domain/port/incomming/GetAffinityProductsUC.java
new file mode 100644
index 0000000..82fa514
--- /dev/null
+++ b/src/main/java/com/example/productaffinity/domain/port/incomming/GetAffinityProductsUC.java
@@ -0,0 +1,11 @@
+package com.example.productaffinity.domain.port.incomming;
+
+import com.example.productaffinity.domain.model.Product;
+import reactor.core.publisher.Mono;
+
+import java.util.List;
+
+// Input Port for resolving similar products to a requested product
+public interface GetAffinityProductsUC {
+    Mono<List<Product>> getAffinityProducts(String productId);
+}
diff --git a/src/main/java/com/example/productaffinity/domain/port/outcoming/AffinityProductsIdsPort.java b/src/main/java/com/example/productaffinity/domain/port/outcoming/AffinityProductsIdsPort.java
new file mode 100644
index 0000000..5225f71
--- /dev/null
+++ b/src/main/java/com/example/productaffinity/domain/port/outcoming/AffinityProductsIdsPort.java
@@ -0,0 +1,4 @@
+package com.example.productaffinity.domain.port.outcoming;
+
+public class AffinityProductsIdsPort {
+}
diff --git a/src/main/java/com/example/productaffinity/domain/port/outcoming/ProductDetailsPort.java b/src/main/java/com/example/productaffinity/domain/port/outcoming/ProductDetailsPort.java
new file mode 100644
index 0000000..2e2fcd8
--- /dev/null
+++ b/src/main/java/com/example/productaffinity/domain/port/outcoming/ProductDetailsPort.java
@@ -0,0 +1,9 @@
+package com.example.productaffinity.domain.port.outcoming;
+
+import reactor.core.publisher.Mono;
+
+import java.util.Collection;
+
+public interface ProductDetailsPort {
+    Mono<Collection<String>> findAffinityProductIds(String productId);
+}
diff --git a/src/main/java/com/example/productaffinity/domain/service/SimilarProductsService.java b/src/main/java/com/example/productaffinity/domain/service/SimilarProductsService.java
new file mode 100644
index 0000000..f166806
--- /dev/null
+++ b/src/main/java/com/example/productaffinity/domain/service/SimilarProductsService.java
@@ -0,0 +1,20 @@
+package com.example.productaffinity.domain.service;
+
+import com.example.productaffinity.domain.model.Product;
+import com.example.productaffinity.domain.port.incomming.GetAffinityProductsUC;
+import org.springframework.stereotype.Service;
+import reactor.core.publisher.Mono;
+
+import java.util.List;
+
+@Service
+public class SimilarProductsService implements GetAffinityProductsUC {
+
+    public SimilarProductsService() {
+    }
+
+    @Override
+    public Mono<List<Product>> getAffinityProducts(String productId) {
+        return null;
+    }
+}