This text discusses how to use HashiCorp Vault's PKI secrets engine to generate SSL certificates for a Spring Boot application, and then configure SSL hot reload in the application to automatically update web servers with new certificates. The process involves setting up the PKI secrets engine on Vault, deploying Vault Agent to write the certificates to files, configuring the application properties to reference these files, and starting the application. When the certificate nears expiration, Vault Agent requests a new certificate and writes it to the files, causing the Spring application to automatically reload itself with the new certificate without requiring manual intervention or downtime.