01Why this order, and not another one

MERN gets taught a hundred different ways, but most beginners burn weeks because they start with the flashy part — React — before they understand what it's talking to. This roadmap goes in the order things actually depend on each other: Node → Express → MongoDB → React, then tying them together.

That's the opposite of "front-end first," and it's deliberate: a backend you understand makes React's data-fetching make sense instead of feeling like magic.

02The four checkpoints, in plain terms

Tap any card for what it actually is and what "good enough to move on" looks like.

03What the pieces look like wired together

This is the moment it stops feeling like four separate subjects: a minimal Express route that reads from MongoDB and sends JSON back, which React then fetches and renders.

// the smallest version of "Express talks to Mongo"
const express = require('express');
const app = express();

app.get('/api/trails', async (req, res) => {
  const trails = await Trail.find();
  res.json(trails);
});

app.listen(3000);

And the React side, fetching that same route on load:

function TrailList() {
  const [trails, setTrails] = useState([]);

  useEffect(() => {
    fetch('/api/trails')
      .then(res => res.json())
      .then(setTrails);
  }, []);

  return trails.map(t => <li key={t.id}>{t.name}</li>);
}

04How long this actually takes

"Learn MERN" estimates online are mostly fiction because they ignore how many hours a week someone really has. Set yours honestly below.

05Mistakes worth skipping

06Quick check

Two questions to confirm the route makes sense.