@matt If we have more than one requests are accessing caddy server at the same time , what is is the process caddy used to generate certificates for multiple domains, Sequential or Parallel?
Cert issuance is done in parallel, but there is rate limiting built-in to avoid stampeding.
More detail in the docs:
Francis is right; Caddy can obtain as many certs at once as allowed by rate limits and throttling.
If two clients request a cert for the same domain at the same time, only one cert will be obtained, and both will unblock once the cert is ready.