The Netlify Cache API now has full support for stale-while-revalidate (SWR). This was a previous limitation of the Cache API that has now been lifted, thanks to a request from a customer.
When using fetchWithCache with the swr option, background revalidation is handled automatically. If a response is stale but still within the SWR window, it’s served immediately while a fresh response is fetched and cached in the background.
import { fetchWithCache, DAY, HOUR } from "@netlify/cache";
import type { Config, Context } from "@netlify/functions";
export default async (req: Request, context: Context) => {
const response = await fetchWithCache("https://example.com/expensive-api", {
ttl: 2 * DAY,
swr: HOUR,
tags: ["product"],
});
return response;
};
export const config: Config = {
path: "/api/products",
};
For users who interact directly with cache.match and cache.put, a new needsRevalidation method lets you check whether a cached response is stale and trigger background revalidation manually:
import { needsRevalidation, cacheHeaders, MINUTE, HOUR } from "@netlify/cache";
import type { Config, Context } from "@netlify/functions";
const cache = await caches.open("my-cache");
export default async (req: Request, context: Context) => {
const request = new Request("https://example.com/expensive-api");
const cached = await cache.match(request);
if (cached) {
if (needsRevalidation(cached)) {
context.waitUntil(
fetch(request).then((fresh) => {
const response = new Response(fresh.body, {
headers: {
...Object.fromEntries(fresh.headers),
...cacheHeaders({ ttl: MINUTE, swr: HOUR }),
},
});
return cache.put(request, response);
})
);
}
return cached;
}
const fresh = await fetch(request);
const response = new Response(fresh.body, {
headers: {
...Object.fromEntries(fresh.headers),
...cacheHeaders({ ttl: MINUTE, swr: HOUR }),
},
});
context.waitUntil(cache.put(request, response.clone()));
return response;
};
export const config: Config = {
path: "/api/data",
};
Learn more in the Cache API documentation and the caching overview.