At what stage was it found out that the previously proposed architecture does not fit the goals?

Usually, architecture mismatches with goals become apparent during the pilot implementation or prototyping stage, when key features are being implemented and their functionality is being tested.

It can also manifest during the requirements testing or user feedback analysis stage, when it becomes clear that the architecture does not provide the necessary performance, scalability, or ease of support.

It is important to conduct regular architecture and prototype reviews to identify such issues in a timely manner and adjust the approach.