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MongoDB Examples

By · Reviewed & last updated · Part of MongoDB Tutorial

A handful of MongoDB patterns you reach for over and over - upsert, time series, geospatial, transactions.

MongoDB by example

EXAMPLE
// 1. Upsert
await users.updateOne(
  { email: 'ada@example.com' },
  {
    $set: { name: 'Ada', updatedAt: new Date() },
    $setOnInsert: { createdAt: new Date(), provider: 'email' },
  },
  { upsert: true }
);


// 2. Time-series collection (4.4+)
await db.createCollection('metrics', {
  timeseries: {
    timeField: 'ts',
    metaField: 'tags',
    granularity: 'seconds',
  },
  expireAfterSeconds: 60 * 60 * 24 * 30,   // 30 days TTL
});

await db.collection('metrics').insertOne({
  ts: new Date(),
  tags: { host: 'web1', region: 'syd' },
  cpu: 0.42,
  rss: 184_320_000,
});


// 3. Geospatial queries
await places.createIndex({ loc: '2dsphere' });

await places.insertOne({
  name: 'Bondi Beach',
  loc: { type: 'Point', coordinates: [151.2766, -33.8908] },
});

const within10km = await places.find({
  loc: {
    $nearSphere: {
      $geometry: { type: 'Point', coordinates: [151.2093, -33.8688] },
      $maxDistance: 10_000,
    },
  },
}).toArray();


// 4. Transactions
const session = client.startSession();
try {
  await session.withTransaction(async () => {
    await accounts.updateOne({ _id: from }, { $inc: { balance: -amount } }, { session });
    await accounts.updateOne({ _id: to   }, { $inc: { balance:  amount } }, { session });
    await ledger.insertOne({ from, to, amount, at: new Date() }, { session });
  });
} finally {
  await session.endSession();
}


// 5. Aggregation - top spenders this week
const top = await orders.aggregate([
  { $match: { createdAt: { $gte: new Date(Date.now() - 7 * 86_400_000) } } },
  { $group: { _id: '$customerId', total: { $sum: '$total' }, n: { $sum: 1 } } },
  { $sort: { total: -1 } },
  { $limit: 10 },
]).toArray();


// 6. Bulk write
await users.bulkWrite([
  { insertOne: { document: { email: 'a@x' } } },
  { updateOne: { filter: { email: 'b@x' }, update: { $set: { tier: 'pro' } } } },
  { deleteOne: { filter: { _id: someId } } },
], { ordered: false });

Why it matters

These five patterns - upsert, time series, geospatial, transactions, aggregation - cover most of the non-CRUD work you do with Mongo. Bulk writes are the single biggest perf win when you have batch jobs hitting the same collection.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
// See the lesson body for ready-to-paste queries.
print('MongoDB examples');
Try it Yourself »

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