Capnproto is designed by Kenton, a former Google engineer who did a lot of work with protobufs at Google. I see Capnproto as the spiritual successor of protobuf

Capnproto is designed by Kenton, a former Google engineer who did a lot of work with protobufs at Google. I see Capnproto as the spiritual successor of protobuf, fixing many issues in protobufs. Also, Capnproto is quite extensively used in some Cloudflare products.