Cache invalidation strategies in Express

Introduction

Cache invalidation helps keep stored data fresh and accurate by removing or updating old information.

When you update data on the server and want users to see the latest version.

When cached data becomes outdated after a certain time.

When you want to clear cache after a user logs out to protect privacy.

When you want to improve performance but avoid showing stale data.

When you want to control cache behavior for different types of content.

Syntax

Express

app.use((req, res, next) => {
  res.set('Cache-Control', 'no-cache');
  next();
});

This example shows how to set HTTP headers to control cache behavior in Express.

You can customize cache rules using different Cache-Control directives.

Examples

This tells browsers not to store any cache at all.

Express

res.set('Cache-Control', 'no-store');

This allows caching for 60 seconds before invalidation.

Express

res.set('Cache-Control', 'max-age=60');

This allows shared caches to store the response for 5 minutes.

Express

res.set('Cache-Control', 'public, max-age=300');

This caches data only for the user and requires revalidation before use.

Express

res.set('Cache-Control', 'private, no-cache');

Sample Program

This Express app sets a cache expiration of 10 seconds for all responses. The homepage shows the current time. If you refresh within 10 seconds, the cached response may be used. After 10 seconds, the cache invalidates and the server sends fresh data.

Express

import express from 'express';
const app = express();

// Middleware to set cache control headers
app.use((req, res, next) => {
  // Invalidate cache after 10 seconds
  res.set('Cache-Control', 'public, max-age=10');
  next();
});

app.get('/', (req, res) => {
  res.send(`Current time: ${new Date().toISOString()}`);
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Important Notes

Cache-Control headers are the main way to control cache invalidation in HTTP.

Use short max-age values for frequently changing data.

Remember to test cache behavior using browser DevTools Network tab.

Summary

Cache invalidation keeps data fresh by controlling how long cached data is valid.

Express apps use Cache-Control headers to set cache rules.

Choose the right strategy based on how often your data changes.