Don't specify entire baseUrl

app/javascript/packs/frontend/api.js

@@ -4,7 +4,7 @@ import axios from 'axios';
 //const csrfToken = document.querySelector('meta[name="csrf-token"]').content;
 
 const instance = axios.create({
-  baseURL: 'http://localhost:3000/api/v1',
+  baseURL: '/api/v1',
   timeout: 3000,
   responseType: 'json',
   headers: {post: {'Content-Type': 'application/json'}},