Which description best characterizes a hot standby system that can fail over instantly?

• A. Cold standby is powered off and activated only after a failure
• B. Hot standby runs on a different network path to avoid single point of failure
• C. Warm standby uses manual switchover
• D. It runs concurrently with the primary system and can fail over instantly

Answer: (D)

In a hot standby setup, the backup system is running at the same time as the primary and is kept in near real-time sync so it can take over immediately if the primary fails. The description that the backup “runs concurrently with the primary system and can fail over instantly” matches this idea exactly—the whole point of a hot standby is to have the standby ready to assume control without delay, delivering seamless availability.

Cold standby, by contrast, is powered off and only activated after a failure, which causes downtime. Warm standby is pre-configured and ready but typically requires some manual intervention or time to switch over, so it isn’t instantaneous. Having a backup on a different network path helps avoid a single point of failure, but that doesn’t define the instant failover capability of a hot standby.