| B+-Tree Structure and Invariants | concept | 3 | Open |
| Bloom Filters as LSM Read Accelerators | concept | 3 | Open |
| Clustered vs Secondary Indexes; Covering Indexes | concept | 4 | Open |
| Hash, Bitmap, GIN/GiST: Specialty Indexes | concept | 5 | Open |
| Join Algorithms: Nested Loop, Hash, Sort-Merge | concept | 1 | Open |
| Locking-Based Concurrency: 2PL, Lock Escalation | concept | 2 | Open |
| LSM-Trees: SSTables, Memtables, Compaction | concept | 2 | Open |
| MVCC: How Snapshots Avoid Reader-Writer Contention | concept | 2 | Open |
| Pages, Records, Heap Files, Slotted Pages | concept | 3 | Open |
| Point Lookups, Range Scans, and Why B+-Trees Dominate OLTP | concept | 3 | Open |
| Query Execution Models: Volcano / Iterator, Vectorized, JIT | concept | 2 | Open |
| Statistics, Histograms, and the Cost-Based Optimizer | concept | 2 | Open |
| The Buffer Pool and Page Replacement | concept | 2 | Open |
| Why Databases Care About Disk: Random vs Sequential I/O | concept | 4 | Open |
| Write-Ahead Logging (WAL) and Recovery with ARIES Sketch | concept | 3 | Open |