MongoDB Interview Cheat Sheet

1. What is MongoDB?

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2. What is a document in MongoDB?

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3. What is a collection?

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4. What is a database in MongoDB?

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5. What is BSON?

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6. What is an ObjectId?

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7. What is a schema in MongoDB?

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8. What is the purpose of the find() method?

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9. What is the difference between find() and findOne()?

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10. What does the updateOne() function do?

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11. What is a deleteOne() operation?

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12. What is field projection in MongoDB?

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13. What is an index in MongoDB?

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14. What is a primary key in MongoDB?

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15. What is a replica set?

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16. What is sharding in MongoDB?

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17. What is MongoDB Atlas?

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18. What is the difference between MongoDB and a relational database?

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19. What is the purpose of the $set operator?

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20. What does the $inc operator do?

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21. What is a capped collection and when should it be used?

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22. What is the difference between $push and $addToSet?

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23. What is an embedded document and when is embedding recommended?

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24. What is data referencing in MongoDB?

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25. What is the purpose of the aggregation pipeline?

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26. What is $lookup used for?

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27. What is the difference between insertOne and insertMany?

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28. What is the purpose of TTL indexes?

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29. What is the explain function and why is it useful?

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30. What is a write concern?

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31. What is a read preference?

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32. What is journaling in MongoDB?

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33. What is $regex used for?

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34. What is the difference between save and update?

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35. What is sharding key selection and why is it important?

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36. How does MongoDB handle schema flexibility while still allowing schema validation?

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37. What are the main differences between embedding and referencing in MongoDB?

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38. How do compound indexes improve query performance?

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39. What is an index prefix and why does it matter in compound indexing?

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40. What is the purpose of an aggregation pipeline’s $facet stage?

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41. What is $unwind and why is it used?

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42. What is a covered query in MongoDB?

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43. What is index cardinality and how does it affect performance?

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44. What are multi-key indexes?

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45. What is the difference between $in and $nin in performance?

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46. What is write concern and why is it important?

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47. What is read concern in MongoDB?

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48. How does MongoDB ensure durability during crashes?

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49. What are write-ahead logs (journal files) and how do they work?

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50. What is a MongoDB transaction and when is it needed?

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