diff --git a/03_source/frontend/src/lib/axios.ts b/03_source/frontend/src/lib/axios.ts
new file mode 100644
index 0000000..b291a92
--- /dev/null
+++ b/03_source/frontend/src/lib/axios.ts
@@ -0,0 +1,83 @@
+import type { AxiosRequestConfig } from 'axios';
+import axios from 'axios';
+import { CONFIG } from 'src/global-config';
+
+// ----------------------------------------------------------------------
+
+const axiosInstance = axios.create({ baseURL: CONFIG.serverUrl });
+
+axiosInstance.interceptors.response.use(
+  (response) => response,
+  (error) => Promise.reject((error.response && error.response.data) || 'Something went wrong!')
+);
+
+export default axiosInstance;
+
+// ----------------------------------------------------------------------
+
+export const fetcher = async (args: string | [string, AxiosRequestConfig]) => {
+  try {
+    const [url, config] = Array.isArray(args) ? args : [args];
+
+    const res = await axiosInstance.get(url, { ...config });
+
+    return res.data;
+  } catch (error) {
+    console.error('Failed to fetch:', error);
+    throw error;
+  }
+};
+
+// ----------------------------------------------------------------------
+
+export const endpoints = {
+  chat: '/api/chat',
+  kanban: '/api/kanban',
+  calendar: '/api/calendar',
+  auth: {
+    me: '/api/auth/me',
+    signIn: '/api/auth/sign-in',
+    signUp: '/api/auth/sign-up',
+  },
+  mail: {
+    list: '/api/mail/list',
+    details: '/api/mail/details',
+    labels: '/api/mail/labels',
+  },
+  post: {
+    list: '/api/post/list',
+    details: '/api/post/details',
+    latest: '/api/post/latest',
+    search: '/api/post/search',
+  },
+  product: {
+    list: '/api/product/list',
+    details: '/api/product/details',
+    search: '/api/product/search',
+  },
+  user: {
+    list: '/api/user/list',
+    profile: '/api/user/profile',
+    update: '/api/user/update',
+    settings: '/api/user/settings',
+    details: '/api/user/details',
+  },
+  order: {
+    list: '/api/order/list',
+    profile: '/api/order/profile',
+    update: '/api/order/update',
+    settings: '/api/order/settings',
+    details: '/api/order/details',
+    changeStatus: (orderId: string) => `/api/order/changeStatus?orderId=${orderId}`,
+  },
+  invoice: {
+    list: '/api/invoice/list',
+    profile: '/api/invoice/profile',
+    update: '/api/invoice/update',
+    saveInvoice: (invoiceId: string) => `/api/invoice/saveInvoice?invoiceId=${invoiceId}`,
+    settings: '/api/invoice/settings',
+    details: '/api/invoice/details',
+    changeStatus: (invoiceId: string) => `/api/invoice/changeStatus?invoiceId=${invoiceId}`,
+    search: '/api/invoice/search',
+  },
+};
diff --git a/03_source/frontend/src/lib/firebase.ts b/03_source/frontend/src/lib/firebase.ts
new file mode 100644
index 0000000..6440693
--- /dev/null
+++ b/03_source/frontend/src/lib/firebase.ts
@@ -0,0 +1,19 @@
+import type { FirebaseApp } from 'firebase/app';
+import type { Auth as AuthType } from 'firebase/auth';
+import type { Firestore as FirestoreType } from 'firebase/firestore';
+
+import { getAuth } from 'firebase/auth';
+import { initializeApp } from 'firebase/app';
+import { getFirestore } from 'firebase/firestore';
+
+import { CONFIG } from 'src/global-config';
+
+// ----------------------------------------------------------------------
+
+const isFirebase = CONFIG.auth.method === 'firebase';
+
+export const firebaseApp = isFirebase ? initializeApp(CONFIG.firebase) : ({} as FirebaseApp);
+
+export const AUTH = isFirebase ? getAuth(firebaseApp) : ({} as AuthType);
+
+export const FIRESTORE = isFirebase ? getFirestore(firebaseApp) : ({} as FirestoreType);
diff --git a/03_source/frontend/src/lib/supabase.ts b/03_source/frontend/src/lib/supabase.ts
new file mode 100644
index 0000000..60f780e
--- /dev/null
+++ b/03_source/frontend/src/lib/supabase.ts
@@ -0,0 +1,16 @@
+import type { SupabaseClient } from '@supabase/supabase-js';
+
+import { createClient } from '@supabase/supabase-js';
+
+import { CONFIG } from 'src/global-config';
+
+// ----------------------------------------------------------------------
+
+const isSupabase = CONFIG.auth.method === 'supabase';
+
+const supabaseUrl = CONFIG.supabase.url;
+const supabaseKey = CONFIG.supabase.key;
+
+export const supabase = isSupabase
+  ? createClient(supabaseUrl, supabaseKey)
+  : ({} as SupabaseClient<any, 'public', any>);