Why should you care?

A single API response may need totals, top 5 products, and status breakdown without scanning the collection three times from the client.

See it live — copy this example

Open mongosh or MongoDB Compass, select database nosqlverse, then run the example. Change one field and run again.

db.orders.insertMany([
  { status: "paid", total: 100 },
  { status: "paid", total: 400 },
  { status: "cancelled", total: 50 }
])
db.orders.aggregate([
  { $facet: {
      byStatus: [ { $group: { _id: "$status", n: { $sum: 1 } } } ],
      totals: [ { $group: { _id: null, revenue: { $sum: "$total" } } } ],
      sample: [ { $limit: 2 } ]
  }}
])

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• One $facet outputs an object with byStatus, totals, and sample arrays.
• Each sub-pipeline sees the same input (all orders here).
• Clients get three views in one round trip.

Practice next

1. Run the facet pipeline.
2. Add a $match before $facet to scope a tenant.
3. Add a topOrders sub-pipeline with $sort+$limit.
4. Facet products: price histogram + brand counts.
5. Add a $project after facet to reshape.

Remember

$facet runs parallel sub-pipelines. Great for dashboard payloads. Filter before faceting.

Seller home dashboard

One request returns order counts by status, GMV, and recent orders.

Outcome: Mobile seller app loads the home screen in one call.