diff --git a/wrapper.go b/wrapper.go
index cdd601c..c2470d7 100644
--- a/wrapper.go
+++ b/wrapper.go
@@ -15,6 +15,12 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"sync"
+)
+
+var (
+	storefrontCache     map[int]string
+	storefrontCacheOnce sync.Once
 )
 
 func parseStorefrontID(id string) string {
@@ -22,26 +28,30 @@ func parseStorefrontID(id string) string {
 	if err != nil {
 		panic(err)
 	}
-	type StorefrontMapping struct {
-		Name         string `json:"name"`
-		Code         string `json:"code"`
-		StorefrontId int    `json:"storefrontId"`
-	}
-	var mapping []StorefrontMapping
-	file, err := os.ReadFile("data/storefront_ids.json")
-	if err != nil {
-		panic(err)
-	}
-	err = json.Unmarshal(file, &mapping)
-	if err != nil {
-		panic(err)
-	}
-	for _, element := range mapping {
-		if element.StorefrontId == sfID {
-			return element.Code
+
+	storefrontCacheOnce.Do(func() {
+		type StorefrontMapping struct {
+			Name         string `json:"name"`
+			Code         string `json:"code"`
+			StorefrontId int    `json:"storefrontId"`
 		}
-	}
-	return ""
+		var mapping []StorefrontMapping
+		file, err := os.ReadFile("data/storefront_ids.json")
+		if err != nil {
+			panic(err)
+		}
+		err = json.Unmarshal(file, &mapping)
+		if err != nil {
+			panic(err)
+		}
+
+		storefrontCache = make(map[int]string)
+		for _, element := range mapping {
+			storefrontCache[element.StorefrontId] = element.Code
+		}
+	})
+
+	return storefrontCache[sfID]
 }
 
 func PrepareWrapper(mirror bool) {
diff --git a/wrapper_test.go b/wrapper_test.go
new file mode 100644
index 0000000..1ed21fd
--- /dev/null
+++ b/wrapper_test.go
@@ -0,0 +1,51 @@
+package main
+
+import (
+	"os"
+	"testing"
+)
+
+func setupStorefrontFile() (func(), error) {
+	const filename = "data/storefront_ids.json"
+	originalContent, err := os.ReadFile(filename)
+	originalExists := err == nil
+
+	content := `[{"name":"United States","code":"us","storefrontId":143441},{"name":"China","code":"cn","storefrontId":143465}]`
+	_ = os.MkdirAll("data", 0755)
+	_ = os.WriteFile(filename, []byte(content), 0644)
+
+	teardown := func() {
+		os.Remove(filename)
+		if originalExists {
+			os.WriteFile(filename, originalContent, 0644)
+		}
+	}
+	return teardown, nil
+}
+
+func TestParseStorefrontID(t *testing.T) {
+	teardown, _ := setupStorefrontFile()
+	defer teardown()
+
+	// Verify known ID
+	code := parseStorefrontID("143441-1,29")
+	if code != "us" {
+		t.Errorf("Expected 'us', got '%s'", code)
+	}
+
+	// Verify another known ID
+	code = parseStorefrontID("143465-something")
+	if code != "cn" {
+		t.Errorf("Expected 'cn', got '%s'", code)
+	}
+}
+
+func BenchmarkParseStorefrontID(b *testing.B) {
+	teardown, _ := setupStorefrontFile()
+	defer teardown()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = parseStorefrontID("143441-1,29")
+	}
+}