antigravity-claudekit/skills/ck-databases/SKILL.md

name, description

name	description
ck-databases	Design schemas and write queries for MongoDB and PostgreSQL. Use for database design, SQL/NoSQL queries, aggregation pipelines, indexes, migrations, replication, performance optimization, psql CLI operations.

ck-databases

Unified guide for working with MongoDB (document-oriented) and PostgreSQL (relational) databases.

When to Use

• Designing database schemas and data models
• Writing queries (SQL or MongoDB query language)
• Building aggregation pipelines or complex joins
• Optimizing indexes and query performance
• Implementing database migrations
• Setting up replication, sharding, or clustering
• Configuring backups and disaster recovery
• Analyzing slow queries and performance issues
• Administering production database deployments

Don't Use When

• ORM/query-builder API work only — refer to the specific library's docs via ck-docs-seeker
• Infrastructure setup for managed database services — use ck-devops

Database Selection Guide

Need	Choose
ACID transactions, complex joins	PostgreSQL
Flexible document schema	MongoDB
Caching, sessions, queues	Redis
Analytics/OLAP workloads	PostgreSQL with proper indexing
1-to-few relationships	MongoDB embedded documents
1-to-many or many-to-many	MongoDB references or PostgreSQL FK

MongoDB Best Practices

• Use embedded documents for 1-to-few relationships
• Reference documents for 1-to-many or many-to-many
• Index frequently queried and sorted fields
• Use aggregation pipeline for complex transformations
• Enable authentication and TLS in production
• Use Atlas for managed hosting

Common patterns:

• CRUD operations with query operators and atomic updates
• Aggregation pipeline stages: $match, $group, $lookup, $project, $sort
• Index types: single field, compound, text, geospatial, TTL
• Atlas search for full-text capabilities

PostgreSQL Best Practices

• Normalize schema to 3NF; denormalize selectively for performance
• Use foreign keys for referential integrity
• Index foreign keys and frequently filtered columns
• Use EXPLAIN ANALYZE to optimize queries
• Regular VACUUM and ANALYZE maintenance
• Connection pooling via pgBouncer for web apps

Key features:

• SELECT, JOINs, subqueries, CTEs, window functions
• psql meta-commands for administration
• EXPLAIN, query optimization, vacuum, index maintenance
• User management, backups, replication, point-in-time recovery

Python Utility Scripts

Available in the skill's scripts/ directory:

# Generate and apply migrations
python scripts/db_migrate.py --db mongodb --generate "add_user_index"
python scripts/db_migrate.py --db postgres --apply

# Backup and restore
python scripts/db_backup.py --db postgres --output /backups/

# Performance analysis
python scripts/db_performance_check.py --db mongodb --threshold 100ms

Performance Optimization Checklist

• Indexes on frequently queried fields
• Compound indexes ordered by selectivity
• EXPLAIN ANALYZE run on slow queries
• Connection pooling configured
• Query result caching with Redis where appropriate
• Pagination instead of full table scans
• Read replicas for read-heavy workloads
• Partitioning for very large tables (PostgreSQL)

Security Checklist

• Authentication enabled (no anonymous access)
• TLS/SSL for connections in production
• Parameterized queries everywhere (never string concatenation)
• Least-privilege database users
• Regular backups tested for restore
• Audit logging enabled for sensitive operations

Resources

• MongoDB: https://www.mongodb.com/docs/
• PostgreSQL: https://www.postgresql.org/docs/