defense-in-depth-validation

Validate data at every layer to make bugs structurally impossible.

• Validate at every layer data passes through
• Catch invalid data before it causes harm
• Make bugs structurally impossible
• Prevent bypass via code paths, mocks, or edge cases

• Entry point validation rejects obvious invalid input
• Business logic validates data relevance to operation
• Environment guards block dangerous context-specific actions
• Debug logging captures context for forensics
• Each layer catches different types of failures
• Multiple layers ensure no single point of failure
• Must validate at every checkpoint in data flow
• Critical: don't stop at one validation point

1. 1.Trace data flow to identify origin and usage points
2. 2.Map all checkpoints where data passes through
3. 3.Add validation at entry, business, environment, and debug layers
4. 4.Test each layer to ensure it catches bypasses
5. 5.Verify each layer catches edge cases and mocks