A hot standby node is a member of a group of nodes (clique), and no virtual processes are running on it (AMPs, Parsing Engines).
The hot standby node waits for its mission, which occurs when a node crashes out of its clique.
Then all the AMPs of the crashed node are immediately migrated to the hot standby node. This happens practically without any loss of performance:
The smart thing about the design is the following: As soon as the crashed node is online again, it becomes the new hot standby node: