Monitoring APIs after deployment is essential to ensure high availability and reliability. It allows for real-time tracking of API performance, identifying and addressing issues, and ensuring that the API meets the needs of users. While adding more features and impressing stakeholders are important, the primary goal of monitoring is to maintain service availability and quality.

Load testing for APIs involves simulating network traffic to understand its behavior under stress. This helps identify how the API performs when subjected to heavy data requests and high network loads.

To ensure that a mobile app continues to function when the API is updated, you should use API versioning. The most common and recommended approach is to use HTTP headers to specify the API version. This allows clients to make requests to the appropriate API version and ensures backward compatibility. Including the API version in the URL can lead to cleaner and more consistent API design.

When using JWT (JSON Web Tokens) for authorization, the token's "Payload" claims can be used to store the user's roles and permissions. The payload is where you can include claims about the user, such as their roles and permissions, which can be checked when authorizing access to resources.

Load testing for APIs focuses on assessing how well the API performs under varying levels of load, such as concurrent users or data volume. Performance testing, on the other hand, encompasses a broader evaluation of the API's overall capabilities, including speed, scalability, security, and more.

Logging can be effectively used in API troubleshooting to track requests and responses. It helps in identifying issues, analyzing traffic, and monitoring performance, which is crucial for debugging and maintaining API functionality.

Automating functional tests ensures that the API functions correctly in a real-world scenario, from start to finish. Functional tests verify that the API performs its intended tasks and provides the expected results, making them critical for ensuring the API's overall reliability and functionality.

In a situation where a client needs continuous real-time updates, GraphQL subscriptions and gRPC streams can be utilized. GraphQL subscriptions enable real-time updates, allowing the server to push data to clients when changes occur. gRPC streams, on the other hand, provide efficient server-client streaming, making them suitable for real-time communication.

The OAuth 2.0 "Client Credentials" flow is used by applications that can securely maintain client secrets. It is suitable for server-to-server communication where the application can confidently store and protect its client credentials, ensuring secure and authorized access to protected resources.

A GraphQL query primarily consists of three main components: Queries (used for read operations), Mutations (used for write operations), and Subscriptions (used for real-time data updates). These components allow clients to request, modify, and receive data from a GraphQL server. The options provided in the question do not accurately represent the main components of a GraphQL query.