Azure keyvault jca needs to visit key vault remotely. For each visit, it also needs an access token, so currently it also gets the access token remotely each time. This is not what we want, because the same access token can be reused, and to get the remote access token is time costly.

Please see the log:
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
c.a.s.keyvault.jca.KeyVaultClient : Getting key for alias: friend
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
c.a.s.keyvault.jca.KeyVaultClient : Getting certificate for alias: friend
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
c.a.s.keyvault.jca.KeyVaultClient : Using Azure Key Vault: https://kv-sp.vault.azure.net/
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
c.a.s.keyvault.jca.KeyVaultClient : Getting key for alias: friend
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
c.a.s.keyvault.jca.KeyVaultClient : Getting certificate for alias: friend
c.a.security.keyvault.jca.AuthClient : Getting access token using client ID / client secret
o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8443 (https) with context path ''
c.a.s.b.s.w.SpringBootWebappApplication : Started SpringBootWebappApplication in 117.996 seconds (JVM running for 118.846)