Appian Cloud's High Availability (HA) architecture is designed to ensure business continuity and minimize downtime. A key advantage, as stated in option B, is the continuous, synchronous replication of data and transactions across multiple nodes. This redundancy eliminates single points of failure, ensuring that if one node becomes unavailable, the system can continue operating using another node.

Another significant advantage, detailed in option D, is the guaranteed service level for recovery. Appian Cloud HA provides a Recovery Time Objective (RTO) of less than 15 minutes and a Recovery Point Objective (RPO) of less than 1 minute. This means the service will be restored quickly with minimal data loss, which is a critical benefit for mission-critical applications.

A. An Appian Cloud HA instance uses multiple availability zones within the same geographic region for low-latency replication, not different regions. Multi-region setups are for Disaster Recovery (DR).

C. A standard Appian Cloud HA configuration is composed of three active application server nodes, not two. This ensures a quorum can be maintained in the event of a single node failure.

1. Appian Corporation. (2024). Appian Cloud High Availability. Appian Documentation.

Section: Overview: "Appian Cloud High Availability (HA) provides a multi-node

redundant architecture to protect your Appian instance from a single point of failure... Data and transactions are continuously replicated across the active nodes to achieve redundancy." (Supports option B).

Section: Recovery: "Recovery Time Objective (RTO): Less than 15 minutes" and "Recovery Point Objective (RPO): Less than 1 minute." (Supports option D).

Section: Architecture: "The standard Appian Cloud configuration includes three application servers... Each node is located in a different data center (availability zone) within the same geographical region." (Refutes options A and C).