Step-by-step articles on MongoDB, part of our NoSQL & Caching collection.
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MongoDB stores data as JSON-like documents in collections . If you know SQL, most concepts map directly; the big shift is designing around how data is read rather than normalising everything. Vocabulary Table → collection . Row → document (stored as BSON, whic...
"Schemaless" doesn't mean "no design". In MongoDB, schema design starts from one question: what does the application read together? Embed when data is read together and owned by the parent { "_id": "ord_42", "customerId": 7, "status": "paid", "shippingAddress"...
Without an index, MongoDB scans every document in a collection ( COLLSCAN ). Indexes make queries fast, and compound index order matters as much as in SQL. Creating indexes await orders.createIndex({ customerId: 1 }); await orders.createIndex({ status: 1, crea...
The aggregation pipeline processes documents through a series of stages, each transforming the output of the previous one. It's MongoDB's answer to SQL's GROUP BY , joins and reporting queries. Revenue per day const revenue = await orders.aggregate([ { $match:...
MongoDB itself is flexible about document shape. Mongoose adds schemas, validation, defaults and helpers on top of the official driver, which brings structure to application code. Defining a model import mongoose from 'mongoose'; await mongoose.connect(process...
Single-document updates in MongoDB have always been atomic. Since version 4.0 (replica sets) and 4.2 (sharded clusters), MongoDB also supports multi-document ACID transactions. Do you need one? Often a good document design avoids the need. Updating an order an...
Change streams let your application subscribe to changes in a collection, database or entire cluster. Instead of polling, you get each insert, update and delete as it happens. Watching a collection const stream = orders.watch( [{ $match: { operationType: { $in...
If your application data already lives in MongoDB, you can store embeddings in the same documents and query them with Atlas Vector Search , without running a separate vector database. Store embeddings with your documents await articles.insertOne({ title: 'Rese...
Flexible documents are great until a bug writes price: "free" or forgets a required field. MongoDB can validate documents on every insert and update, regardless of which application wrote them. Creating a collection with a validator await db.createCollection('...
skip() and limit() are the obvious way to paginate, but skip(100000) still walks past 100,000 documents. Range-based pagination keeps every page equally fast. Range (keyset) pagination // First page const page = await posts .find({ status: 'published' }) .sort...
