No architect can single-handedly determine the overall risk of a system.

 The reason for this is two-fold. 

First, a single architect might miss or overlook a risk area, and very few architects have full knowledge of every part of the system. 

This is where risk storming can help.

• Risk storming is a collaborative exercise used to determine architectural risk

within a specific dimension. 

Common dimensions (areas of risk) include

unproven technology, performance, scalability, availability (including transitive

dependencies), data loss, single points of failure, and security.

https://riskstorming.com/