mongodb-usage

MongoDB Best Practices MCP Limitation This MCP operates in READ-ONLY mode. No write, update, or delete operations are possible. Schema Design Patterns Embedding vs Referencing Embed when: Data is accessed together frequently Child documents are bounded (won't grow unbounded) One-to-few relationships Data doesn't change frequently Reference when: Data is accessed independently Many-to-many relationships Documents would exceed 16MB limit Frequent updates to referenced data Common Patterns Subset pattern: Store frequently accessed subset in parent, full data in separate collection. Bucket pattern: Group time-series data into buckets (e.g., hourly readings in one document). Computed pattern: Store pre-computed values for expensive calculations. Index Strategies Index Guidelines Index fields used in queries, sorts, and aggregation $match stages Compound indexes support queries on prefix fields Covered queries (all fields in index) are fastest Too many indexes slow writes Index Types Single field: Basic index on one field Compound: Multiple fields, order matters for queries Multikey: Automatically created for array fields Text: Full-text search on string content TTL: Auto-expire documents after time period ESR Rule For compound indexes, order fields by: E quality (exact match fields) S ort (sort order fields) R ange (range query fields like $gt, $lt) Aggregation Pipeline Performance Tips Put $match and $project early to reduce documents Use $limit early when possible Avoid $lookup on large collections without indexes Use $facet for multiple aggregations in one query Common Stages // Filter documents { $match : { status : "active" } } // Reshape documents { $project : { name : 1 , total : { $sum : "$items.price" } } } // Group and aggregate { $group : { _id : "$category" , count : { $sum : 1 } } } // Sort results { $sort : { count : - 1 } } // Join collections { $lookup : { from : "orders" , localField : "_id" , foreignField : "userId" , as : "orders" } } Connection Best Practices Connection String Formats Atlas: mongodb+srv://user:pass@cluster.mongodb.net/database Local: mongodb://localhost:27017/database Replica set: mongodb://host1,host2,host3/database?replicaSet=rs0 Connection Pooling Use connection pooling in applications (default in drivers) Set appropriate pool size for your workload Don't create new connections per request Anti-Patterns to Avoid Unbounded arrays: Arrays that grow without limit Massive documents: Documents approaching 16MB Too many collections: Use embedding instead Missing indexes: Queries doing collection scans $where operator: Use aggregation instead for security Storing files in documents: Use GridFS for large files