Why does Envoy use BoringSSL?
BoringSSL is a slimmed down TLS implementation maintained by Google. Getting TLS right is very, very hard. Envoy has chosen to align with BoringSSL so as to obtain access to the world class experts that Google employs to work on this code base. In short: if BoringSSL is good enough for Google’s production systems it is good enough for Envoy and the project will not offer first class support for any other TLS implementation.