Lesson 01
Database Query Performance for Backend Systems Explained
Decision: separate user, application, pool, database, wait, and retry evidence before changing a production workload.
System Design topic cluster
Database Query Performance
Production database performance guides for query plans, statistics, indexes, MVCC maintenance, lock contention, partition pruning, compatible migrations, and incident response.
9 ordered lessons
Build an evidence-driven database performance loop.
Move from user impact through plans, statistics, storage, contention, safe remediation, and verified production recovery.
-
-
Lesson 02
PostgreSQL EXPLAIN and Query Plans Explained
Decision: read estimates, actual work, loops, buffers, and plan shape without treating EXPLAIN ANALYZE as passive.
-
Lesson 03
Query Planner Statistics and Cardinality Estimation Explained
Decision: distinguish stale statistics from skew, correlation, sampling, and prepared-plan behavior.
-
Lesson 04
Composite, Covering, and Partial Indexes Explained
Decision: shape indexes around predicates and ordering while accounting for writes, visibility, WAL, and maintenance.
-
Lesson 05
MVCC, VACUUM, and Table Bloat Explained
Decision: use dead-tuple, vacuum, transaction-age, storage, and workload evidence before disruptive maintenance.
-
Lesson 06
Database Lock Contention and Long Transactions Explained
Decision: reconstruct blocker chains and preserve rollback and side-effect boundaries before canceling sessions.
-
Lesson 07
Table Partitioning and Partition Pruning Explained
Decision: partition only when lifecycle or pruning evidence outweighs planning, routing, and operational cost.
-
Lesson 08
Zero-Downtime Database Schema Migrations Explained
Decision: use compatible expand, migrate, verify, and contract phases with bounded locks and resumable backfills.
-
Lesson 09
Production Slow Query Troubleshooting for Backend Systems
Decision: move from user impact to normalized workloads, waits, plans, mitigation, and evidence-based recovery.