Why is my subdomain 20 times slower than the domain?

I have 2 very simple pages and both are set up with the same caching rule:

The first, the main domain, is delivered directly by a worker with embedded HTML.
The header, Cf-Cache-Status: HIT
The response time is around 30ms

The second is delivered by a CF managed subdomain directly from an R2 bucket.
The header, Cf-Cache-Status: DYNAMIC (I have never seen HIT)
The response time can be up to 1.3 seconds.

I’m testing this from Sydney and the bucket is in APAC.
As I said, both have the same caching rules.
The second always misses the cache, how do I fix this please?

Hi there,

DYNAMIC means Cloudflare does not consider the asset eligible for cache, but you can use cache rules to force it.

Take care.