developing-with-mongodb

name	developing-with-mongodb
description	Use when working with the agent implements MongoDB NoSQL database solutions with document modeling, aggregation pipelines, and Mongoose ODM. Use when building document-based applications, designing schemas, writing aggregations, or implementing NoSQL patterns.
metadata	{"author":"doanchienthangdev"}

Developing with MongoDB

Quick Start

// Schema with Mongoose
import mongoose, { Schema, Document } from 'mongoose';

interface IUser extends Document {
  email: string;
  profile: { firstName: string; lastName: string };
  createdAt: Date;
}

const userSchema = new Schema<IUser>({
  email: { type: String, required: true, unique: true, lowercase: true },
  profile: {
    firstName: { type: String, required: true },
    lastName: { type: String, required: true },
  },
}, { timestamps: true });

userSchema.index({ email: 1 });
export const User = mongoose.model<IUser>('User', userSchema);

Features

Feature	Description	Guide
Document Schema	Type-safe schema design with Mongoose	Embed related data, use references for large collections
CRUD Operations	Create, read, update, delete with type safety	Use findById, findOne, updateOne, deleteOne
Aggregation Pipelines	Complex data transformations and analytics	Chain $match, $group, $lookup, $project stages
Indexing	Query optimization with proper indexes	Create compound indexes matching query patterns
Transactions	Multi-document ACID operations	Use sessions for operations requiring atomicity
Change Streams	Real-time data change notifications	Watch collections for inserts, updates, deletes

Common Patterns

Repository Pattern with Pagination

async findPaginated(filter: FilterQuery<IUser>, page = 1, limit = 20) {
  const [data, total] = await Promise.all([
    User.find(filter).sort({ createdAt: -1 }).skip((page - 1) * limit).limit(limit),
    User.countDocuments(filter),
  ]);
  return { data, pagination: { page, limit, total, totalPages: Math.ceil(total / limit) } };
}

Aggregation Pipeline

const stats = await Order.aggregate([
  { $match: { status: 'completed', createdAt: { $gte: startDate } } },
  { $group: { _id: '$userId', total: { $sum: '$amount' }, count: { $sum: 1 } } },
  { $sort: { total: -1 } },
  { $limit: 10 },
]);

Transaction for Order Creation

const session = await mongoose.startSession();
try {
  session.startTransaction();
  await Product.updateOne({ _id: productId }, { $inc: { stock: -quantity } }, { session });
  const order = await Order.create([{ userId, items, total }], { session });
  await session.commitTransaction();
  return order[0];
} catch (error) {
  await session.abortTransaction();
  throw error;
} finally {
  session.endSession();
}

Best Practices

Do	Avoid
Design schemas based on query patterns	Embedding large arrays in documents
Create indexes for frequently queried fields	Using $where or mapReduce in production
Use lean() for read-only queries	Skipping validation on writes
Implement pagination for large datasets	Storing large files directly (use GridFS)
Set connection pool size appropriately	Hardcoding connection strings
Use transactions for multi-document ops	Ignoring index usage in explain plans
Add TTL indexes for expiring data	Creating too many indexes (write overhead)

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