| # | title | topic | type | difficulty |
|---|---|---|---|---|
| 1 | Hidden classes: the shape game | Patterns & Performance | Multiple choice | Hard |
| 2 | Four duplicates checks, one is optimal | Patterns & Performance | Multiple choice | Hard |
| 3 | Order-preserving dedupe at scale | Patterns & Performance | Coding | Hard |
| 4 | The lazy singleton pattern | Patterns & Performance | Coding | Hard |