You can create a firewall handling a 1Gb/s link with OpenBSD, but passed that, it's quite limited. Even with top end hardware, we could not go past ~5Gb/s with

You can create a firewall handling a 1Gb/s link with OpenBSD, but passed that, it's quite limited. Even with top end hardware, we could not go past ~5Gb/s with simple pf rules and after a lot of tweaking. With FreeBSD or Linux, we got the 10Gb/s out of the box with similar rules. That's for the network part. As for userland application, it's also slower than Linux or FreeBSD, I remember benching some OpenSSL/LibreSSL based application. On the same hardware I was at 200 transaction/s (transaction ~= RSA signature) with Linux/FreeBSD, with OpenBSD I was at 150 transaction/s, so significantly slower.