This endpoint returns the high availability status and current leader instance of Vault.
$ curl \
http://127.0.0.1:8200/v1/sys/leader
{
"ha_enabled": true,
"is_self": false,
"leader_address": "https://127.0.0.1:8200/",
"leader_cluster_address": "https://127.0.0.1:8201/",
"performance_standby": false,
"performance_standby_last_remote_wal": 0
}