LESSON 3 Lesson Plan 1 MongoDB Document and $jsonSchema, embedding and referencing, owned / snapshot / current copy, arrays, transactions, gaming applications · 3–12 2 Redis Key types and families, TTL and invalidation, leaderboard, memory, and eviction · 13–17 3 Comparison with a Relational Schema Unavailability vs. Loss: What Remains in PostgreSQL · Slides 18–19; Conclusions and Questions · 20–21. Appendix ▶ P1–P8: Commands for the slides ▶ P9–P17: Practical Patterns