Skillshub database-mongodb

Expert rules for schema design, indexing, and performance in MongoDB. Use when designing MongoDB schemas, creating indexes, or optimizing NoSQL query performance. (triggers: **/*.ts, **/*.js, **/*.json, mongo, mongoose, objectid, schema, model)

install

source · Clone the upstream repo

git clone https://github.com/ComeOnOliver/skillshub

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/ComeOnOliver/skillshub "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/HoangNguyen0403/agent-skills-standard/database-mongodb" ~/.claude/skills/comeonoliver-skillshub-database-mongodb && rm -rf "$T"

manifest: skills/HoangNguyen0403/agent-skills-standard/database-mongodb/SKILL.md

source content

MongoDB Best Practices

Priority: P0 (CRITICAL)

Guidelines

Schema Design:
- Embed vs Reference:
  - Embed (1:Few): Addresses, Phone Numbers. Optimization: Read locality.
  - Reference (1:Many/Infinity): Logs, Activity History. Optimization: Document size limits (16MB).
- Bucket Pattern: For time-series or high-cardinality "One-to-Many", bucket items into documents (e.g.,
```
DailyLog
```
  ).
Indexing:
- ESR Rule: Equality, Sort, Range. Order your index keys
```
(status, date, price)
```
  if you query
```
status='A'
```
  , sort by
```
date
```
  , filter
```
price > 10
```
  .
- Text Search: Use
```
$text
```
  search instead of
```
$regex
```
  for keywords.
```
$regex
```
  is slow (linear scan) unless anchored (
```
^prefix
```
  ).
- Covered Queries: Project only indexed fields to avoid fetching the document (
```
PROJECTION
```
  is key).
- Explain Plan: Target
```
nReturned
```
  /
```
keysExamined
```
  ratio of ~1. If
```
docsExamined
```
  >>
```
nReturned
```
  , index is inefficient.
Sharding (Horizontal Scale):
- Shard Key: Avoid monotonically increasing keys (e.g.,
```
Timestamp
```
  ,
```
ObjectId
```
  ) for high-write workloads (creates "Hot Shards"). Use Hashed Sharding or high-cardinality natural keys.
Performance:
- Avoid
  skip()
  : Use
```
_id
```
  or sort-key based pagination (
```
bucket_id > last_id
```
  ).
```
skip(10000)
```
  scans 10000 docs.
- Aggregation: Prefer Aggregation Framework (
```
$match
```
  ,
```
$group
```
  ) over bringing data to client (JS).
Operations:
- Write Concern: Understand
```
w:1
```
  (Ack) vs
```
w:majority
```
  (Safe).
- Transactions: Use only when ACID across multiple documents is stricter than performance needs.

Anti-Patterns

No unbounded arrays: Use
```
$push
```
with
```
$slice
```
or redesign using the 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 are frequently queried.

Skillshub database-mongodb

MongoDB Best Practices

Priority: P0 (CRITICAL)

Guidelines

Anti-Patterns

References