A render URL describes the configuration, not the artwork. Replace a layer image and every URL stays exactly the same, which is what makes caching safe, and what makes a stale picture possible.
Clear it
- Replace the layer image.
- Invalidate the cache for that model.
- The CDN copy expires behind it.
Until then, visitors keep getting the picture that was already composed.
1
Replace the artwork
A new file goes onto the layer image. The URL that asks for the render does not change.
immediate
2
Composed pictures are invalidated
Every cached picture built from that image is dropped. It is rebuilt on the next request for it.
immediate
3
The CDN copy expires
The edge keeps its own copy on its own lifetime. Until it expires, visitors get the old picture.
takes longest
Only what someone asked for is rebuilt. A combination nobody has requested since the change was never
composed in the first place, so it is current the moment it is first opened.
What to reuse
Troubleshooting
The old picture is still showing after invalidation
The edge copy has its own lifetime. Check with a cache-busting query string first: if that shows the new artwork, it is the CDN and it will catch up.
Only some combinations updated
Only the combinations someone has requested since the change were re-composed. The rest compose on first request and will be current.
