Example: Todo App

This example demonstrates how to build a production-ready Todo API using @express-route-cache. We will focus on Automatic Invalidation and SWR.

1. Setup

First, initialize your cache with an adapter (we'll use Memory for this example).

import express from 'express';
import { createCache, createMemoryAdapter } from '@express-route-cache/core';

const app = express();
app.use(express.json());

const cache = createCache({
  adapter: createMemoryAdapter(),
  staleTime: 60, // 1 minute fresh
  swr: true      // Background refresh
});

2. Listing Todos (Cached)

We use cache.route() without any arguments to use the global defaults. This route will be cached at /api/todos.

app.get('/api/todos', cache.route(), (req, res) => {
  // Imagine a slow DB call here
  res.json([
    { id: 1, text: 'Buy milk', completed: false },
    { id: 2, text: 'Build cache library', completed: true }
  ]);
});

3. Adding a Todo (Auto-Invalidate)

When we add a new todo, we want the list cache (/api/todos) to be cleared immediately. By setting autoInvalidate: true, the library will automatically increment the version for this route pattern after a successful POST.

app.post('/api/todos', cache.route({ autoInvalidate: true }), (req, res) => {
  // 1. Save to DB...
  // 2. Cache for '/api/todos' is automatically invalidated!
  res.status(201).json({ id: 3, ...req.body });
});

4. Updating a Todo (Targeted Invalidation)

When updating a specific todo, we want to invalidate both the item and the list.

app.patch('/api/todos/:id', (req, res) => {
  const { id } = req.params;

  // Manual programmatic invalidation
  res.on('finish', async () => {
    if (res.statusCode === 200) {
      // Invalidate both the specific item and the parent list
      await cache.invalidateRoute(`/api/todos/${id}`, '/api/todos');
    }
  });

  res.json({ id, ...req.body });
});

💡 Key Takeaways

1. Zero Work on GET: Just add cache.route() and your API is instantly faster.
2. Safe Mutations: Using autoInvalidate or res.on('finish') ensures you never serve stale data after a database change.
3. High Performance: All invalidations shown here are O(1) operations.