Relayd(8) is a multi-purpose daemon in OpenBSD that can be used as a load balancer, application layer gateway, and transparent proxy. It is capable of monitoring groups of hosts for high availability. Managing relayd(8) involves reading the man pages and configuring the relayd.conf file. You can set up simple HTTP relay configurations, encrypt HTTP relay using TLS, and implement load balancing and failover. Fallback server options are available for automatic or manual switch. You can also relay multiple FQDNs and pathnames. It is possible to improve security and privacy by managing HTTP headers. Log management options allow customization of log files and inclusion of additional information.
https://www.tumfatig.net/2023/using-openbsd-relayd8-as-an-application-layer-gateway/