mongodump --uri="mongodb://localhost:27017" --db=shopDB --out=./backup

await db.admin().command({ fsync: 1, lock: true });
// ... take filesystem snapshot here ...
await db.admin().command({ fsyncUnlock: 1 });

# Back up an entire deployment
mongodump --uri="mongodb://localhost:27017" --out=./backup

# Back up a specific collection
mongodump --uri="mongodb://localhost:27017" --db=shopDB --collection=orders --out=./backup

# Back up with a query filter
mongodump --db=shopDB --collection=orders --query='{"status":"completed"}' --out=./backup

# Restore an entire dump directory
mongorestore --uri="mongodb://localhost:27017" ./backup

# Restore into a different database name
mongorestore --uri="mongodb://localhost:27017" --nsFrom="shopDB.*" --nsTo="shopDB_staging.*" ./backup

# Drop existing collections before restoring
mongorestore --drop ./backup

mongoexport --uri="mongodb://localhost:27017" --db=shopDB --collection=users --out=users.json

mongoimport --uri="mongodb://localhost:27017" --db=shopDB --collection=users --file=users.json

# Import with upsert on a unique field
mongoimport --db=shopDB --collection=users --file=users.json --mode=upsert --upsertFields=email

mongodump --db=shopDB --collection=orders --out=./bson-backup
# Produces: bson-backup/shopDB/orders.bson + orders.metadata.json

mongoexport --db=shopDB --collection=products --out=products.json --jsonArray --pretty

# Export to CSV with specific fields
mongoexport --db=shopDB --collection=users --type=csv --fields=name,email,age --out=users.csv

# Import from CSV
mongoimport --db=shopDB --collection=users --type=csv --headerline --file=users.csv

1. Restore the most recent full snapshot before the target time
2. Replay oplog entries up to the exact target timestamp
3. Verify data consistency post-restore

# Example: AWS EBS snapshot after fsyncLock
aws ec2 create-snapshot --volume-id vol-0123456789abcdef0 --description "MongoDB backup $(date +%F)"

# Restore to a staging environment first for validation
mongorestore --uri="mongodb://staging-host:27017" ./backup

# Restore a single collection from a full dump
mongorestore --nsInclude="shopDB.orders" ./backup

// Compare document counts between source and restored target
const sourceCount = await sourceDb.collection('orders').countDocuments();
const restoredCount = await targetDb.collection('orders').countDocuments();

if (sourceCount !== restoredCount) {
  console.error('⚠️ Document count mismatch after restore!');
}

// MongoDB's built-in validation command
const result = await db.collection('orders').validate({ full: true });

// Add a new field with a default value to all existing documents
await db.collection('users').updateMany(
  { role: { $exists: false } },
  { $set: { role: 'customer' } }
);

// Rename a field across the collection
await db.collection('users').updateMany(
  {},
  { $rename: { 'fullname': 'name' } }
);

const fcv = await db.admin().command({ getParameter: 1, featureCompatibilityVersion: 1 });
console.log(fcv.featureCompatibilityVersion);

# Dump from source cluster
mongodump --uri="mongodb+srv://user:pass@source-cluster.mongodb.net" --out=./migration

# Restore to target cluster
mongorestore --uri="mongodb+srv://user:pass@target-cluster.mongodb.net" ./migration

// 1. Initial bulk copy (source → target)
const docs = await sourceDb.collection('orders').find({}).toArray();
await targetDb.collection('orders').insertMany(docs);

// 2. Stream ongoing changes during the cutover window
const changeStream = sourceDb.collection('orders').watch();
changeStream.on('change', async (change) => {
  if (change.operationType === 'insert') {
    await targetDb.collection('orders').insertOne(change.fullDocument);
  }
  // handle update/delete operationTypes similarly
});