You are a developer in the HR department working on designing a workflow for vacation...

Interactive buttons are the appropriate component because the approval action is directly associated with an existing Slack message. Slack specifically recommends making notification messages actionable when the recipient is expected to perform an immediate follow-up activity. Approval scenarios are a canonical example: a message can contain Approve/Reject buttons, and the resulting interaction payload can be processed by the application backend. After the manager selects Approve, the application can persist the approval to the external vacation-management service and then modify the Slack message to represent the new state. Slack's chat.update method is explicitly designed to update previously posted, non-ephemeral messages and is suitable for reflecting state changes after an interactive action. Interactive messages therefore provide both the decision mechanism and a clean method for maintaining visible state. A reaction could signal intent but does not provide the same structured interactive workflow. Global shortcuts and slash commands are primarily workflow entry points and are unnecessary when the actionable business object is already represented by a message. This aligns directly with Design the Interactive Flow of Your App, including interactive message components and updating application surfaces after user actions.