Shared Packages in Micro Frontend Monorepo — Complete Guide

Your Micro Frontend has a silent bug and you don't know it yet. The user logs in on the Auth MFE. The auth token gets saved to the Redux store. They navigate to Products — a different MFE loaded via Module Federation. The Products page says they're not logged in. Why? Because Products MFE created its own Redux store instance. Auth MFE has a separate instance. Two stores. Two states. Completely out of sync. This is the #1 problem teams hit when they build Micro Frontends without shared packages. What are shared packages? Internal libraries inside your monorepo that ALL MFEs consume. Instead of each MFE building its own API layer, its own Redux store, and its own UI components, you build them ONCE in packages/ and import everywhere. In this article, I break down the 3 packages that hold a production MFE monorepo together: 1. @myapp/api — Shared API Layer Full axios instance with request interceptors (JWT token attachment) and response interceptors (401 handling + token refresh) Failed re