REST Cache not recreated

[yfr]

We are using MapCache with the Google Cloud Storage REST cache. We have set an auto_expire to 60 for example. This should recreate the requested tiles after 60 seconds. This does not work. The tiles are never recreated.

In the client, I see these response data. Cache-Control: max-age=60 is always 60.

Date: Tue, 26 Oct 2021 09:50:23 GMT
Server: Apache/2.4.25 (Debian)
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: POST, GET, OPTIONS
Cache-Control: max-age=60
Expires: Tue, 26 Oct 2021 09:51:23 GMT
Content-Length: 3079
Content-Type: image/png

For tests, I switched to a disk cache. There, the recreation works just fine, and the following response is given to the client.

Date: Tue, 26 Oct 2021 09:50:06 GMT
Server: Apache/2.4.25 (Debian)
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: POST, GET, OPTIONS
Last-Modified: Tue, 26 Oct 2021 09:50:07 GMT
Cache-Control: max-age=59
Expires: Tue, 26 Oct 2021 09:51:06 GMT
Content-Length: 3658
Content-Type: image/png

Cache-Control: max-age=60 will count down to the time to recreate the tile. Notice also the Last-Modified header, which is not present in the mapCache response with REST cache.

We are guessing that the Last-Modified from the REST API is not used. Can someone help here? Do we need to add something special to the REST cache config?