[kjaftaedi]

I get the feeling OP is the one being interviewed.

Mortgage rates change frequently.

The bank likely deals with this exact scenario on a regular basis and should have an established procedure in place.

[dx034]

Source of Truth should (in my opinion) be used in many sectors but even finance doesn't use it everywhere. Having each data point originate in only one system helps a lot with data quality but is complex to introduce in existing systems.

[todaysAI]

No, no interview. He's a friend of mine but I kept his problem in my head to possibly provide some solution.

[in9]

You underestimate what how unknowledgeable a small financial institution can be.