Explanation
The correct answer is: "Resiliency is about recovering from failures without downtime or data loss." Service resiliency, in the context of cloud-native applications, is the ability of a service or system to recover from failures and continue functioning without downtime or data loss. It involves designing and implementing mechanisms to handle failures, such as network outages, hardware failures, or software errors, in a way that minimizes the impact on the overall system. The goal of resiliency isto ensure that the application or service can continue to operate and provide a certain level of functionality, even in the face of failures. This typically involves techniques such as redundancy, fault tolerance, and graceful degradation. By implementing resiliency measures, a cloud-native application can recover and adapt to failures, maintain availability, and preserve data integrity. The other statements are not accurate regarding service resiliency: Resiliency is not about not bringing a service to a functioning state after a failure. Instead, it is about recovering from failures and ensuring continued functionality. Resiliency is not about avoiding failures entirely. While it is desirable to prevent failures, resiliency focuses on the ability to handle and recover from failures when they do occur.
Resiliency testing is not limited to a test environment. It is important to test and validate the resiliency measures in both test environments and production environments to ensure the application can effectively handle failures in real-world scenarios.

OCI API Gateway supports the following authentication methods for accessing an API deployment3:
HTTP Basic: The client sends a username and password with each request. The credentials are validated against a user database in Oracle Identity Cloud Service (IDCS).
API Key: The client sends an API key with each request. The API key is validated against a list of keys stored in IDCS or OCI Vault.
OAuth: The client obtains an access token from an authorization server (such as IDCS) and sends it with each request. The access token is validated against the authorization server and optionally checked for required scopes.
JWT Token: The client obtains a JSON Web Token (JWT) from an identity provider (such as IDCS or OCI IAM) and sends it with each request. The JWT is validated against the identity provider's public key and optionally checked for required claims. SAML Token is not a valid authentication method for accessing an OCI API Gateway deployment. SAML is an XML-based standard for exchanging authentication and authorization data between different parties, such as a service provider and an identity provider4. SAML tokens are typically used for web browser single sign-on (SSO) scenarios, not for API access4.

End-to-end testing is a technique that involves checking the entire user flow as well as the moving parts of a cloud native app, ensuring that there are no high-level discrepancies3. End-to-end testing simulates real user scenarios and validates the functionality, performance, reliability, and security of the app from start to finish3. End-to-end testing has several benefits, such as3:
Comprehensive testing: You can test your app as a whole and verify that all the components work together as expected.
User-centric testing: You can test your app from the user's perspective and ensure that it meets the user's needs and expectations.
Quality assurance: You can test your app in a realistic environment and identify any issues or defects before releasing it to the users.

The correct answer is: "Once rotated, older key versions can be used for encryption until they are deleted." The statement that is NOT valid about rotating keys in the OCI Vault service is: "Once rotated, older key versions can be used for encryption until they are deleted." In the OCI Vault service, when you rotate a master encryption key (MEK), a new key version is automatically generated. However, once a key is rotated and a new version is created, the older key versions are no longer usable for encryption. The purpose of key rotation is to ensure that the encryption keys are regularly updated and that older keys are no longer used to protect sensitive data. This enhances security by minimizing the impact of potential key compromises. The other statements mentioned are valid: Both software and hardware security module (HSM)-protected MEKs can be rotated. This provides flexibility in choosing the type of MEK and ensures that key rotation can be performed regardless of the encryption method used. Each key version is tracked internally with separate unique OCIDs (Oracle Cloud Identifiers). This allows for easy management and tracking of different key versions within the OCI Vault service. In summary, the statement that is NOT valid is the one suggesting that older key versions can still be used for encryption until they are deleted. Key rotation is designed to ensure the use of the latest key version and to retire older key versions to enhance security.

Explanation
A rolling update is a deployment strategy that gradually replaces the old version of an application with the new version without any downtime4. OKE supports rolling updates by using the kubectl rollout command4. A rolling update allows you to roll back to the previous version if something goes wrong with the new version4.
Therefore, using a rolling update strategy with kubectl ensures that you can roll back to the previous version of your Python application if the new image does not work once deployed.Verified References: Deploy Oracle Container Engine for Kubernetes