Databases Advanced
Query Plan Investigator
Investigate PostgreSQL query plans, cardinality gaps, scan choices, join amplification, and rollout evidence.
- Time
- 9-12 minutes
- Concept
- SQL query planning and cardinality
Backend concept
Database Reliability
Partition tradeoffs, replica consistency, recovery objectives, deadlocks, and transaction isolation.
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Key takeaway
Partition tradeoffs, replica consistency, recovery objectives, deadlocks, and transaction isolation. Start with the related games below when you want to turn the definition into practice.
Why this matters
Database behavior during partitions, lag, lock contention, and recovery determines whether critical invariants survive failures.
How to practice
Choose explicit consistency, routing, recovery, and retry policies for each failure mode.
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Local review for this concept
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Learning objectives
- Compare estimated and actual plan rows.
- Connect selectivity to scan and join choices.
- Validate query changes across representative workloads.
- Order composite index columns from real predicates.
- Match partial indexes to stable active subsets.
- Connect MVCC and partition choices to operations.
Common mistakes to avoid
- Reading cost as elapsed milliseconds.
- Adding indexes without checking selectivity.
- Validating only one parameter value.
- Leading a composite index with the wrong predicate.
- Treating partitions as automatic speedups.
- Disabling vacuum to reduce load.
Games for Database Reliability
Start with the first game, then use local review history to revisit missed decisions.
Databases Advanced
Index & Storage Strategy Lab
Choose composite and partial indexes while accounting for MVCC churn, bloat, and partition lifecycle.
- Time
- 8-11 minutes
- Concept
- Index and storage strategy
Reliability Advanced
Slow Query & Change War Room
Triage blocking chains, slow-query regressions, expand-contract changes, and resource-safe database rollouts.
- Time
- 10-12 minutes
- Concept
- Production database incident response
Databases Advanced
Partition Tradeoff Commander
Choose explicit consistency or availability behavior for concrete network-partition scenarios.
- Time
- 7-10 minutes
- Concept
- CAP theorem and partition-time tradeoffs
Databases Advanced
Replica Consistency Router
Route reads across primary and replicas while respecting lag, freshness contracts, failover, and workload isolation.
- Time
- 8-12 minutes
- Concept
- Read replicas and consistency-aware routing
Databases Intermediate
Recovery Objective Drill
Translate RPO and RTO into backup, point-in-time recovery, restore testing, and isolation decisions.
- Time
- 7-10 minutes
- Concept
- Database backup and restore objectives
Databases Advanced
Deadlock Detective
Read waits-for cycles, choose safe victims, retry complete transactions, and prevent recurring deadlocks.
- Time
- 7-11 minutes
- Concept
- Database deadlocks and lock ordering
Databases Advanced
Transaction Isolation Arena
Defend database invariants from concurrent requests by choosing transactions, locks, constraints, snapshot reads, and optimistic concurrency.
- Time
- 7-10 minutes
- Concept
- Database transactions, isolation anomalies, locks, and invariant protection
Databases Advanced
Database Engine & Capacity Lab
Connect durability, MVCC, plan evidence, and connection budgets.
- Time
- 10-12 minutes
- Concept
- database engine capacity
Databases Advanced
Database Failover & Contention War Room
Recover pool, lock, replication, and failover incidents without losing business truth.
- Time
- 10-12 minutes
- Concept
- database failover and contention