To handle and store sensitive data essential for your application's core functionality, here are the best practices: 1. **Encryption**: Use strong encryption for data at rest and in transit. Store encryption keys securely in protected custom settings, metadata, or named credentials. 2. **Authentication and Authorization**: Authenticate and authorize requests before processing privileged actions, especially when accessing or modifying sensitive data. 3. **Secure Storage**: Avoid storing sensitive data in public settings or unencrypted fields. Use protected custom metadata or encrypted custom objects with securely stored keys. 4. **Data Redaction**: Redact sensitive data in logs and ensure it is not exposed in debug logs or URLs. 5. **Cryptography**: Use supported cryptography APIs and avoid custom cryptography implementations. 6. **Access Control**: Follow the principle of least privilege, granting users only the permissions they need. 7. **Secure Coding Practices**: Validate and sanitize user inputs to prevent vulnerabilities like SQL injection and XSS. Use encoding functions where needed. 8. **Documentation and Disclosure**: Keep a record of sensitive data processed or stored and disclose storage locations and third-party sharing practices to customers. 9. **Compliance**: Follow industry-specific regulations like HIPAA or PCI DSS, if applicable. 10. **Audits and Reviews**: Regularly conduct security audits and reviews to identify and fix vulnerabilities. These steps will help ensure the security, confidentiality, and integrity of sensitive data in your application.