Database

What is PostgreSQL # PostgreSQL is a powerful open-source relational database known for its reliability and extensibility, supporting rich data types, full-text search, JSON, and geospatial processing.

Finding slow queries # Enable the slow-query log: log_min_duration_statement Analyze plans with EXPLAIN ANALYZE Watch pg_stat_statements for the most frequent SQL Common performance killers # Full table scans: missing indexes or conditions that can’t use them Implicit type casts: functions on indexed columns disable the index N+1 queries: querying row-by-row inside a loop Large-offset pagination: OFFSET 1000000 gets slower as you page Fixes # Rewrite SQL: drive big tables with small result sets (join order) Use indexes wisely: covering and composite indexes Denormalize judiciously: precomputed summary tables Summary # SQL tuning is about understanding the execution plan. Locate the bottleneck first, then fix it — don’t blindly add indexes.

Why backups matter # Data is the core asset of any system. Hardware failure, human error, ransomware — any incident can cause irrecoverable loss. Data without a backup is not data.

Why indexes matter # Without an index, table scans are O(n) — queries degrade quickly as data grows. A good index brings lookups down to O(log n).