🚀 Edge caching

[spencerwooo]

🚀 Performance improvements with edge caching

Folder listing, thumbnail, search, etc., are now cached with Vercel's edge function caching. You should experience extremely faster load speed for these routes, especially folder listings. (Note: the thumbnails themselves are not cached to follow Vercel's fair use policy, only the URL pointing to the thumbnails are cached.)

The cache is valid for 60 seconds on the edge. - This means you won't see your newly added files for at least 60 seconds after your files are done uploading.

If you want to manually purge the cache of your site, you can do so by triggering a redeployment manually.

The cache is automatically purged upon a new deployment being created. If you ever need to invalidate the CDN cache, you can always re-deploy. Further reading: https://vercel.com/docs/concepts/edge-network/caching.

🛠 Technical details

Relevant headers:

Cache-Control: max-age=0, s-maxage=60, stale-while-revalidate

You can check for response headers x-vercel-cache to see whether your request is responsed by a cache hit (fast 🐰), or fresh revalidated data (slow 🐢).

Cache miss

Most often, no cache is present at the edge when someone first visits a route. This is presented as cache miss, where the response header x-vercel-cache is set to MISS. In this scenario, fresh data is requested from the upstream API, and you will experience a slow load speed (compared to other scenarios).

Cache hit

After the route is requested, Vercel will cache the function response at the edge. When a second request on the same route is triggered, Vercel will respond with the cache instead of requesting data from the upstream for a second time. This is presented as cache hit, where the response header x-vercel-cache is set to HIT. You will experience an instant response.

Cache stale

If the cache is present for longer than 60 seconds, on the request triggered, Vercel will respond with the stale cache, setting x-vercel-cache to STALE, and perform a new request to the upstream API. In this case, the following response is guaranteed to be fresh, and Vercel will update the cache on the edge accordingly. You will experience an instant response for both requests.

[Android-KitKat]

👀 好耶！缓存终于来了。
Cache stale 的情况，也就是说刷新两次才会看到最新内容吗？

[spencerwooo]

https://vercel.com/docs/concepts/functions/edge-caching#stale-while-revalidate

Which tells our CDN: serve from cache, but update it, if requested after 1 second 10 minutes.

也就是 10 分钟后的请求，如果发现 stale 了，先返回 cache 的 response，同时更新 cache，这样下一次 response 是最新内容。

[Android-KitKat]

我发现个小问题，如果 STALE 的缓存在超过一个小时后被访问，那么 @microsoft.graph.downloadUrl 是无效的。
然后 在线浏览 和 下载按钮 就会出错，需要再次刷新才能使用。Σ( ￣□￣||)<

所以 stale-while-revalidate 设置为 31天，驱动器项目 可能仍会存在，但其中的 @microsoft.graph.downloadUrl 一定不可用。

|柱|ω・`) 我觉得也许还能再优化一下？

[spencerwooo]

确实，@microsoft.graph.downloadUrl 的有效时间是 1 小时是吧？应该也设置 cache 有效时间。

[Android-KitKat]

确实，@microsoft.graph.downloadUrl 的有效时间是 1 小时是吧？应该也设置 cache 有效时间。

对，文档写是 1小时。