Stale-While-Revalidate (SWR)

Latency spikes are the enemy of a great user experience. @express-route-cache uses SWR to ensure your users never wait for a database refresh.

How it Works

When a request arrives for a stale entry (older than staleTime but younger than gcTime):

1. Instant HIT: The server immediately serves the stale data from the cache.
2. Background Refresh: The server continues to execute your Express handler in the background.
3. Cache Update: Once the handler returns fresh data, the cache is updated for the next request.

Enabling SWR

SWR is disabled by default. You can enable it globally or per-route:

// Global
const cache = createCache({
  swr: true,
  staleTime: 60, // Fresh for 60s
  gcTime: 3600,   // Kept for 1 hour
});

// Per-route override
app.get('/slow-api', cache.route({ swr: true }), handler);

Benefits

• Zero Latency Spikes: Users always get an instant response.
• Improved Uptime: Even if your database is momentarily slow or down, the cache can serve stale data while attempting a refresh.