Cryptographic keys applied in data safety procedures like encryption, authentication, and digital signing need to be managed securely; a key management system is necessarily required. Generations, storing, distribution, rotation, revocation, access control of these keys controlled under the system safeguard the data safely, securely and within the expectations of requirements from laws like GDPR, HIPAA, and PCI-DSS. Effective KMS operations ensure operational effectiveness, prevent data breaches, and ensure safe data. There are multiple KMS solutions, which come in the form of cloud-based and on-premises, each with their unique advantages and disadvantages. The top solutions are IBM Security Key Lifecycle Manager, Microsoft Azure Key Vault, Google Cloud KMS, and AWS KMS. With several strong algorithms used to set access limits, rotate keys, and check how they are being used, the best practices of key management in reducing security risks are put in place. The KMS proves helpful for health care systems, ensuring confidentiality and integrity of patient data in wireless sensor networks and Internet of Things-based monitoring systems. The study further shows the applications of KMS to enable IoT devices in industrial monitoring, structural health, and e-health. In such fields, privacy of private information is ensured through strong security and encryption. Resource-constrained devices and lightweight encryption halt the addition of security frameworks to IoT networks. The research looks at distributed databases as alternatives but further calls for a need for a centralized system regarding data management, security, and scalability.