What characteristic is essential for a backend to be considered highly available?

To be considered highly available, a backend must exhibit characteristics that ensure its operational continuity and reliability, particularly during failures or maintenance events. Redundant data storage is a critical element of this because it enables the system to maintain access to data even if specific components fail. By having multiple copies of data stored in different locations or systems, the architecture ensures that if one storage node becomes unavailable, the system can still access the data from another node without interruption.

This redundancy can take various forms, such as data replication across servers or geographical locations, distributed databases, or cloud storage solutions that provide automatic failover capabilities. The essence of high availability is to minimize downtime and ensure seamless access to the services provided by the backend.

Other options, like a single point of failure, manual intervention for access, and high latency communication, detract from the concept of high availability. A single point of failure introduces risk, as the failure of one component can lead to complete system breakdown. Manual intervention for access can create delays and hinder system availability, while high latency communication can lead to performance issues, both of which are not conducive to a highly available backend. Consequently, the characteristic of redundant data storage stands out as the essential feature that supports a highly available architecture.