The cache theory only explains the delay in the update here https://www.cloudflare.com/ips-v4
It doesn’t explain the delay in the update here: https://api.cloudflare.com/client/v4/ips which is why I’m saying there doesn’t appear to be a single source of truth. The API endpoint does not appear to be cached:
curl -i https://api.cloudflare.com/client/v4/ips
HTTP/2 200
date: Fri, 09 Apr 2021 16:13:55 GMT
content-type: application/json
set-cookie: __cfduid=dae902c223bef87219ca17f5878394fa31617984835; expires=Sun, 09-May-21 16:13:55 GMT; path=/; domain=.api.cloudflare.com; HttpOnly; SameSite=Lax; Secure
cf-ray: 63d50687184e5df6-BNA
cache-control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
etag: W/"fb21705459fea38d23b210ee7d67b753"
expires: Sun, 25 Jan 1981 05:00:00 GMT
strict-transport-security: max-age=31536000
cf-cache-status: DYNAMIC
cf-request-id: 095902686f00005df6bf1da000000001
expect-ct: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
pragma: no-cache
x-content-type-options: nosniff
x-frame-options: SAMEORIGIN
set-cookie: __cflb=0H28vgHxwvgAQtjUGU4vq74ZFe3sNVUZcsNPLKto2Wq; SameSite=Lax; path=/; expires=Fri, 09-Apr-21 18:43:56 GMT; HttpOnly
set-cookie: __cfruid=0da42b6cf7d6909609e41893a0bce63708a3eaba-1617984835; path=/; domain=.api.cloudflare.com; HttpOnly; Secure; SameSite=None
server: cloudflare
{"result":{"ipv4_cidrs":["173.245.48.0\/20","103.21.244.0\/22","103.22.200.0\/22","103.31.4.0\/22","141.101.64.0\/18","108.162.192.0\/18","190.93.240.0\/20","188.114.96.0\/20","197.234.240.0\/22","198.41.128.0\/17","162.158.0.0\/15","104.16.0.0\/12","172.64.0.0\/13","131.0.72.0\/22"],"ipv6_cidrs":["2400:cb00::\/32","2606:4700::\/32","2803:f800::\/32","2405:b500::\/32","2405:8100::\/32","2a06:98c0::\/29","2c0f:f248::\/32"],"etag":"fb21705459fea38d23b210ee7d67b753"},"success":true,"errors":[],"messages":[]}