Resolved
The issues with upstream caching are now resolved.
Monitoring
From 16:45 to 18:30 UTC we experienced delays in the caching of upstream packages. Our engineers identified a fix for this issue and the backlog of awaiting upstream caching requests has now been processed.
Investigating
We have identified an issue causing delays in caching of upstream packages. Uploads and downloads of packages remain unaffected. Our engineers are investigating.