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database-design

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Description

Covers schema design, migrations, query optimization, indexing strategies, and normalization tradeoffs.

Tool Access

This skill is limited to using the following tools:

ReadWriteEditGlobGrepBash(psql:*sqlite3:*mysql:*)
Supporting Assets
View in Repository
references/indexing.md
references/migrations.md
references/query-optimization.md
references/schema-design.md
Skill Content

Database Skill

Domain knowledge for database administration and development. Covers schema design, migrations, query optimization, and indexing strategies.

When to Use This Skill

  • Designing new tables or modifying existing schemas
  • Writing or reviewing database migrations
  • Optimizing slow queries
  • Planning index strategies
  • Evaluating normalization vs denormalization tradeoffs

Key Reference Files

FileUse When
schema-design.mdCreating tables, choosing keys, audit patterns
migrations.mdWriting safe, reversible migrations
query-optimization.mdDebugging slow queries, N+1 detection
indexing.mdChoosing index types, composite index order

Quick Reference

Primary Key Selection

TypeUse WhenAvoid When
UUID v4Distributed systems, no sequential exposureNeed sortability, space-constrained
ULIDNeed sortability + uniquenessLegacy system compatibility
Serial/IdentitySingle database, simple use caseDistributed writes, ID exposure concerns

Migration Safety

Safe (online):     ADD COLUMN (nullable), ADD INDEX CONCURRENTLY, CREATE TABLE
Unsafe (offline):  ADD COLUMN NOT NULL (without default), DROP COLUMN, RENAME

Index Decision Tree

High cardinality + equality lookups  → B-tree (default)
Low cardinality + many values        → Consider partial index
Array/JSON containment               → GIN
Geometric/range queries              → GiST
Exact equality only                  → Hash (rare)

Core Principles

  1. Data integrity first - Constraints catch bugs that code misses
  2. Plan for scale - Design decisions are expensive to change
  3. Measure before optimizing - Use EXPLAIN ANALYZE, not intuition
  4. Backward compatibility - Migrations must not break running code

Related Skills

  • See foundations for universal code quality principles
  • See infrastructure for connection pooling and deployment patterns
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Last CommitFeb 21, 2026

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