Review struct and mapping usage in this contract:
```
${{CONTRACT_CODE}}
```
Data Structures: ${{DATA_STRUCTURES}}
Security analysis:
1. Struct packing efficiency
2. Mapping key security
3. Nested mapping risks
4. Delete operation handling
5. Default value assumptions
6. Storage layout for upgrades
7. Enumeration patterns
8. Memory vs storage
9. Tight packing vulnerabilities
10. Recommended patterns
Include storage optimization guide.Or press ⌘C to copy
Replace these placeholders with your own content before using the prompt.
[{CONTRACT_CODE][{DATA_STRUCTURES]