HPKP is indeed quite rare. But I am very worried to see that you are pinning end-entity keys and have only a single backup pin. If you want to pin end-entity

HPKP is indeed quite rare. But I am very worried to see that you are pinning end-entity keys and have only a single backup pin. If you want to pin end-entity keys, I recommend pinning at least three backup keys, using both RSA and ECDSA of varying key sizes. You have to be very concerned with bricking your site from either losing your backup keys, or CAs/browsers rejecting your backup keys because cryptographic standards have changed. Pinning end-entity keys is not for the faint-hearted. Cool product, by the way.