databases

What the source does

• FilesystemUndeclared2 observations, not in its own description
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesNot pinnedSome versions float
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

.coverage

plugins/ai-ml-tools/skills/ai-multimodal

plugins/ai-ml-tools/skills/context-engineering

plugins/ai-ml-tools/skills/google-adk-python

plugins/backend-tools/skills/backend-development

plugins/backend-tools/skills/better-auth

shutil.rmtree(backup_path)

shutil.rmtree(restore_path)

.coverage

verify=False

verify=False

verify=False

verify=False

pytest, pytest-cov, pytest-mock

pytest, pytest-cov, pytest-mock, mongomock

// - atlasAdmin: full access

Audit 0.4.1 · source sha d655ab03f566 · 27 Oct 2026Report an issue or request a re-scan

• Publishermrgoonie GitHub userOwner of the repository this skill is read from
• Source foldermrgoonie/claudekit-skills/.claude/skills/databasesThe exact folder we audited
• LicenceNot declaredAs the repository states it
• Commit pinned for this verdictd655ab03f566A new audit runs when the source changes
• Repository statusNot archivedLast push 207 days ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Work with MongoDB (document database, BSON documents, aggregation pipelines, Atlas cloud) and PostgreSQL (relational database, SQL queries, psql CLI, pgAdmin). Use when designing database schemas, writing queries and…

---
name: databases
description: Work with MongoDB (document database, BSON documents, aggregation pipelines, Atlas cloud) and PostgreSQL (relational database, SQL queries, psql CLI, pgAdmin). Use when designing database schemas, writing queries and aggregations, optimizing indexes for performance, performing database migrations, configuring replication and sharding, implementing backup and restore strategies, managing database users and permissions, analyzing query performance, or administering production databases.
license: MIT
---

# Databases Skill

Unified guide for working with MongoDB (document-oriented) and PostgreSQL (relational) databases. Choose the right database for your use case and master both systems.

## When to Use This Skill

Use when:
- 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
- Managing database users and permissions
- Analyzing slow queries and performance issues
- Administering production database deployments

## Database Selection Guide

### Choose MongoDB When:
- Schema flexibility: frequent structure changes, heterogeneous data
- Document-centric: natural JSON/BSON data model
- Horizontal scaling: need to shard across multiple servers
- High write throughput: IoT, logging, real-time analytics
- Nested/hierarchical data: embedded documents preferred
- Rapid prototyping: schema evolution without migrations

**Best for:** Content management, catalogs, IoT time series, real-time analytics, mobile apps, user profiles

### Choose PostgreSQL When:
- Strong consistency: ACID transactions critical
- Complex relationships: many-to-many joins, referential integrity
- SQL requirement: team expertise, reporting tools, BI systems
- Data integrity: strict schema validation, constraints
- Mature ecosystem: extensive tooling, extensions
- Complex queries: window functions, CTEs, analytical workloads

**Best for:** Financial systems, e-commerce transactions, ERP, CRM, data warehousing, analytics

### Both Support:
- JSON/JSONB storage and querying
- Full-text search capabilities
- Geospatial queries and indexing
- Replication and high availability
- ACID transactions (MongoDB 4.0+)
- Strong security features

## Quick Start

### MongoDB Setup

```bash
# Atlas (Cloud) - Recommended
# 1. Sign up at mongodb.com/atlas
# 2. Create M0 free cluster
# 3. Get connection string

# Connection
mongodb+srv://user:[email protected]/db

# Shell
mongosh "mongodb+srv://cluster.mongodb.net/mydb"

# Basic operations
db.users.insertOne({ name: "Alice", age: 30 })
db.users.find({ age: { $gte: 18 } })
db.users.updateOne({ name: "Alice" }, { $set: { age: 31 } })
db.users.deleteOne({ name: "Alice" })
```

### PostgreSQL Setup

```bash
# Ubuntu/Debian
sudo apt-get install postgresql postgresql-contrib

# Start service
sudo systemctl start postgresql

# Connect
psql -U postgres -d mydb

# Basic operations
CREATE TABLE users (id SERIAL PRIMARY KEY, name TEXT, age INT);
INSERT INTO users (name, age) VALUES ('Alice', 30);
SELECT * FROM users WHERE age >= 18;
UPDATE users SET age = 31 WHERE name = 'Alice';
DELETE FROM users WHERE name = 'Alice';
```

## Common Operations

### Create/Insert
```javascript
// MongoDB
db.users.insertOne({ name: "Bob", email: "[email protected]" })
db.users.insertMany([{ name: "Alice" }, { name: "Charlie" }])
```

```sql
-- PostgreSQL
INSERT INTO users (name, email) VALUES ('Bob', '[email protected]');
INSERT INTO users (name, email) VALUES ('Alice', NULL), ('Charlie', NULL);
```

### Read/Query
```javascript
// MongoDB
db.users.find({ age: { $gte: 18 } })
db.users.findOne({ email: "[email protected]" })
```

```sql
-- PostgreSQL
SELECT * FROM users WHERE age >= 18;
SELECT * FROM users WHERE email = '[email protected]' LIMIT 1;
```

### Update
```javascript
// MongoDB
db.users.updateOne({ name: "Bob" }, { $set: { age: 25 } })
db.users.updateMany({ status: "pending" }, { $set: { status: "active" } })
```

```sql
-- PostgreSQL
UPDATE users SET age = 25 WHERE name = 'Bob';
UPDATE users SET status = 'active' WHERE status = 'pending';
```

### Delete
```javascript
// MongoDB
db.users.deleteOne({ name: "Bob" })
db.users.deleteMany({ status: "deleted" })
```

```sql
-- PostgreSQL
DELETE FROM users WHERE name = 'Bob';
DELETE FROM users WHERE status = 'deleted';
```

### Indexing
```javascript
// MongoDB
db.users.createIndex({ email: 1 })
db.users.createIndex({ status: 1, createdAt: -1 })
```

```sql
-- PostgreSQL
CREATE INDEX idx_users_email ON users(email);
CREATE INDEX idx_users_status_created ON users(status, created_at DESC);
```

## Reference Navigation

### MongoDB References
- **[mongodb-crud.md](references/mongodb-crud.md)** - CRUD operations, query operators, atomic updates
- **[mongodb-aggregation.md](references/mongodb-aggregation.md)** - Aggregation pipeline, stages, operators, patterns
- **[mongodb-indexing.md](references/mongodb-indexing.md)** - Index types, compound indexes, performance optimization
- **[mongodb-atlas.md](references/mongodb-atlas.md)** - Atlas cloud setup, clusters, monitoring, search

### PostgreSQL References
- **[postgresql-queries.md](references/postgresql-queries.md)** - SELECT, JOINs, subqueries, CTEs, window functions
- **[postgresql-psql-cli.md](references/postgresql-psql-cli.md)** - psql commands, meta-commands, scripting
- **[postgresql-performance.md](references/postgresql-performance.md)** - EXPLAIN, query optimization, vacuum, indexes
- **[postgresql-administration.md](references/postgresql-administration.md)** - User management, backups, replication, maintenance

## Python Utilities

Database utility scripts in `scripts/`:
- **db_migrate.py** - Generate and apply migrations for both databases
- **db_backup.py** - Backup and restore MongoDB and PostgreSQL
- **db_performance_ch

Excerpt, first 6,000 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

1. 2026-10-27
   !CAUTION B 81 / 100

   first audit · source d655ab03f566

Questions about databases

• github.com/mrgoonie/claudekit-skills/tree/main/.claude/skills/da — the audited source at commit d655ab03f566 and every finding aboveObserved · 27 Oct 2026

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