What encompasses the services that process requests in a web or mobile application?

The correct choice addresses the specific functions within a web or mobile application that handle incoming requests. Web requests and service calls represent the interactions that occur when a user initiates an action, such as clicking a button or loading a page. These requests are typically sent to a server, where they are processed through various backend services that may fetch data, perform calculations, or interact with databases.

Understanding this concept is critical in application development and monitoring. It highlights the flow of data and how services interact with each other to fulfill user requests, making it essential for performance management and troubleshooting.

The other options, while relevant to the overall architecture of an application, do not specifically denote the processes that manage requests. User interface components refer to the elements users interact with, but they do not encapsulate the back-end processing. Message queues are used to manage communication between services but are not the entities that directly process requests. Database transactions are crucial for data integrity and management but represent a different layer of application functionality focused on data storage and retrieval rather than the handling of requests themselves.