defense-in-depth

Validate data at every layer to make bugs structurally impossible.

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

• Entry point validation rejects obvious invalid input
• Business logic validates data relevance
• Environment guards block dangerous operations
• Debug logging captures context for forensics
• Each layer catches different failure cases
• Bypasses are structurally impossible
• Must validate at every layer
• No single validation point is sufficient

1. 1.Trace data flow to identify origin and usage
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 no bypass exists
5. 5.Verify each layer catches edge cases