Asked about Validating at the boundary
Where should validation happen?
An answer that works
At every boundary where data enters from somewhere you do not control, and only there. Past that point everything downstream can assume the shape is correct, which keeps the checks in one place instead of scattered and drifting.
Reading an answer is not being able to give one. The section that teaches this is Validating at the boundary, 6 hours of Typing & validation.
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