Answer Posted / Romesh Kumar Singh

To find duplicate data in MongoDB, you can use the `aggregate()` function with the `$group` and `$match` stages. Here's an example using JavaScript:
```javascript
db.collection.aggregate([
{ $group : { _id : "$field_to_check", count : { $sum: 1 } } },
{ $match : { count : { $gt: 1 } } }
])
```
Replace `"collection"` with the name of your collection and `"field_to_check"` with the field you want to check for duplicates.

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