The correct answer is Service availability.

Service availability is the security principle that ensures systems and data remain accessible and usable when required for essential business operations. It covers architectural and operational controls such as redundancy, load balancing, autoscaling, failover, backups, and tested disaster recovery procedures that keep applications reachable during peak shopping events and during incident recovery.

Service availability is one of the three pillars of the CIA triad along with Data confidentiality and Data integrity. This question focuses on keeping services reachable and operational rather than on preventing disclosure or ensuring data correctness.

Data confidentiality is about protecting information from unauthorized access. It is important for customer records but it does not by itself ensure that systems remain reachable under high load or during recovery.

Access control concerns who may access resources and what actions they may perform. Access control helps enforce confidentiality and accountability but it does not guarantee availability during peak events or after incidents.

Data integrity ensures the accuracy and consistency of information over its lifecycle. It matters for correct transactions and records but it does not address system reachability or uptime under stress.

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