What is the key advantage of building your own Authorization Server with Spring Authorization Server versus adopting Keycloak?

Spring Authorization Server gives full programmatic control within the familiar Spring ecosystem (Java configuration, Spring Data-backed client/user repositories, custom token customization logic) without deploying and administering a separate, heavier third-party IAM product. The tradeoff is you take on more responsibility for security-critical correctness and keeping up with a still-evolving project, versus Keycloak's mature, battle-tested, feature-rich (MFA, social login, admin console) out-of-the-box offering.