diff --git a/src/APL/has-auth-data.ts b/src/APL/has-auth-data.ts
index 3edc3d3..0901c66 100644
--- a/src/APL/has-auth-data.ts
+++ b/src/APL/has-auth-data.ts
@@ -5,6 +5,10 @@ import { hasProp } from "../has-prop";
  */
 export const hasAuthData = (data: unknown) =>
   hasProp(data, "domain") &&
+  data.domain &&
   hasProp(data, "token") &&
+  data.token &&
   hasProp(data, "appId") &&
-  hasProp(data, "saleorApiUrl");
+  data.appId &&
+  hasProp(data, "saleorApiUrl") &&
+  data.saleorApiUrl;
diff --git a/src/APL/saleor-cloud-apl.test.ts b/src/APL/saleor-cloud-apl.test.ts
new file mode 100644
index 0000000..2579f4f
--- /dev/null
+++ b/src/APL/saleor-cloud-apl.test.ts
@@ -0,0 +1,120 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { AuthData } from "./apl";
+import { SaleorCloudAPL, SaleorCloudAPLConfig } from "./saleor-cloud-apl";
+
+const fetchMock = vi.fn();
+
+vi.stubGlobal("fetch", fetchMock);
+
+const aplConfig: SaleorCloudAPLConfig = {
+  resourceUrl: "https://example.com",
+  token: "token",
+};
+
+const stubAuthData: AuthData = {
+  domain: "example.com",
+  token: "example-token",
+  saleorApiUrl: "https://example.com/graphql/",
+  appId: "42",
+  jwks: "{}",
+};
+
+describe("APL", () => {
+  afterEach(() => {
+    vi.resetModules();
+    vi.restoreAllMocks();
+  });
+
+  describe("SaleorCloudAPL", () => {
+    describe("set", () => {
+      it("Successful save of the auth data", async () => {
+        fetchMock.mockResolvedValue({
+          status: 200,
+          json: async () => ({ result: "ok" }),
+          ok: true,
+        });
+
+        const apl = new SaleorCloudAPL(aplConfig);
+        await apl.set(stubAuthData);
+
+        expect(fetchMock).toBeCalledWith(
+          "https://example.com",
+
+          {
+            body: JSON.stringify({
+              saleor_app_id: "42",
+              saleor_api_url: "https://example.com/graphql/",
+              jwks: "{}",
+              domain: "example.com",
+              token: "example-token",
+            }),
+            headers: {
+              "Content-Type": "application/json",
+              Authorization: "Bearer token",
+            },
+            method: "POST",
+          }
+        );
+      });
+
+      it("Raise error when register service returns non 200 response", async () => {
+        fetchMock.mockResolvedValue({
+          status: 500,
+          ok: false,
+        });
+
+        const apl = new SaleorCloudAPL(aplConfig);
+
+        await expect(apl.set(stubAuthData)).rejects.toThrow(
+          "Fetch returned with non 200 status code 500"
+        );
+      });
+    });
+
+    describe("get", () => {
+      describe("Read existing auth data", () => {
+        it("Read existing auth data", async () => {
+          fetchMock.mockResolvedValue({
+            status: 200,
+            ok: true,
+            json: async () => ({
+              saleor_app_id: stubAuthData.appId,
+              saleor_api_url: stubAuthData.saleorApiUrl,
+              jwks: stubAuthData.jwks,
+              domain: stubAuthData.domain,
+              token: stubAuthData.token,
+            }),
+          });
+
+          const apl = new SaleorCloudAPL(aplConfig);
+
+          expect(await apl.get(stubAuthData.saleorApiUrl)).toStrictEqual(stubAuthData);
+
+          expect(fetchMock).toBeCalledWith(
+            "https://example.com/aHR0cHM6Ly9leGFtcGxlLmNvbS9ncmFwaHFsLw", // base64 encoded api url
+            {
+              headers: {
+                "Content-Type": "application/json",
+                Authorization: "Bearer token",
+              },
+              method: "GET",
+            }
+          );
+        });
+
+        it("Return undefined when unknown domain requested", async () => {
+          fetchMock.mockResolvedValue({
+            status: 404,
+            ok: false,
+            json: async () => undefined,
+          });
+
+          const apl = new SaleorCloudAPL(aplConfig);
+
+          expect(await apl.get("http://unknown-domain.example.com/graphql/")).toBe(undefined);
+        });
+      });
+    });
+  });
+});
diff --git a/src/APL/saleor-cloud-apl.ts b/src/APL/saleor-cloud-apl.ts
index a04298b..e2192aa 100644
--- a/src/APL/saleor-cloud-apl.ts
+++ b/src/APL/saleor-cloud-apl.ts
@@ -10,6 +10,11 @@ export type SaleorCloudAPLConfig = {
 };
 
 const validateResponseStatus = (response: Response) => {
+  if (response.status === 404) {
+    debug("Auth data not found");
+
+    throw new Error("Auth data not found");
+  }
   if (!response.ok) {
     debug("Response failed with status %s", response.status);
 
@@ -56,8 +61,8 @@ export class SaleorCloudAPL implements APL {
   }
 
   private getUrlForDomain(saleorApiUrl: string) {
-    // API URL has to be base64 encoded
-    return `${this.resourceUrl}/${btoa(saleorApiUrl)}`;
+    // API URL has to be base64url encoded
+    return `${this.resourceUrl}/${Buffer.from(saleorApiUrl).toString("base64url")}`;
   }
 
   async get(saleorApiUrl: string): Promise<AuthData | undefined> {
@@ -68,10 +73,20 @@ export class SaleorCloudAPL implements APL {
       headers: { "Content-Type": "application/json", ...this.headers },
     }).catch((error) => {
       debug("Failed to reach API call:  %s", error?.message ?? "Unknown error");
-      throw new Error(`Attempt in fetch the data resulted with error: ${error}`);
+      return undefined;
     });
 
-    validateResponseStatus(response);
+    if (!response) {
+      debug("No response from the API");
+      return undefined;
+    }
+
+    try {
+      validateResponseStatus(response);
+    } catch {
+      debug("Response status not valid");
+      return undefined;
+    }
 
     const parsedResponse = (await response.json().catch((e) => {
       debug("Failed to parse response: %s", e?.message ?? "Unknown error");