Database MongodbSAFE

A collection of Agent Skills Standard and Best Practice for Programming Languages, Frameworks that help our AI Agent follow best practies on frameworks and programming laguages

The instruction file, verbatim from the audited commit — this is the text the model reads, and the surface the audit's instruction layer examines. Quoted here so you can judge it without cloning anything.

---
name: database-mongodb
description: Apply MongoDB data-modeling, indexing, and query rules from access patterns. Use when designing schemas, choosing embed vs reference, or tuning MongoDB query behavior.
metadata:
  triggers:
    files:
    - '**/*.ts'
    - '**/*.js'
    - '**/*.json'
    keywords:
    - mongo
    - mongoose
    - objectid
    - schema
    - model
  upstream:
    - name: mongodb
      source: github
      repo: mongodb/mongo
      pinned: "8.0.0"
      tag_pattern: "^r(\\d+\\.\\d+\\.\\d+)$"
      reviewed: "2026-06-17"
---
# MongoDB Best Practices

## **Priority: P0 (CRITICAL)**

## Rules

- Model from access patterns: data read together should usually live together.
- Embed for bounded one-to-few data; reference for unbounded growth or independent lifecycle.
- Build indexes for real queries, not theoretical flexibility. Use ESR ordering for equality -> sort -> range compound indexes.
- Use transactions only when single-document guarantees are insufficient.

## Verify

- [ ] Embed vs reference choice matches cardinality and lifecycle.
- [ ] Compound index order matches equality -> sort -> range access.
- [ ] Large pagination uses cursor patterns, not deep `skip()`.
- [ ] Explain output supports the chosen indexes; review `keysExamined` and `docsExamined`.
- [ ] Unbounded arrays and hot shard keys were reviewed.

## Anti-Patterns

- **No unbounded arrays**: Use `$push` with `$slice` or redesign using Bucket Pattern.
- **No client-side filtering**: Project only needed fields; never fetch full docs to filter in memory.
- **No deep nesting**: Keep nesting ≤4 levels; flatten paths that frequently queried.
- **No index cargo cult**: each index must map to a read path and write tradeoff.

## References

- [Framework Map](../references/framework-map.md)
- [Best Practices Guide](references/best-practices.md)
- [Anti-Patterns](references/anti-patterns.md)
- [Postgres vs Mongo Comparison](references/postgres-comparison.md)

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

What the source does

Filesystem

none-observed

Network

none-observed

Shell

none-observed

Dependencies

pinned

Secrets in source

none-found

Findings (0)

No findings outside the package's declared scope.

Gates applied: no_behavioural_pass.