Top 100 MongoDB Interview Questions for 5+ Years of Experience

Basic MongoDB Questions

1. What is MongoDB, and how does it differ from traditional relational databases?
2. Explain the concept of BSON in MongoDB.
3. What are the key advantages of using MongoDB over a relational database?
4. What is the structure of a MongoDB document?
5. How do you insert data into MongoDB? Explain insertOne() and insertMany().
6. What are the differences between find() and aggregate() in MongoDB?
7. What is the role of collections in MongoDB?
8. How do you delete a document in MongoDB? Explain deleteOne() and deleteMany().
9. How do you update data in MongoDB? What is the difference between updateOne() and updateMany()?
10. What is a primary key in MongoDB?

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Intermediate MongoDB Questions

1. Explain the concept of indexes in MongoDB. Why are they important?
2. What are compound indexes in MongoDB? How do they improve query performance?
3. What is the purpose of the _id field in MongoDB documents?
4. How does MongoDB handle transactions? Explain ACID properties in MongoDB.
5. Explain the differences between embedded documents and referenced documents.
6. What is the purpose of sharding in MongoDB?
7. Explain replica sets in MongoDB. How does MongoDB achieve high availability?
8. What is journaling in MongoDB?
9. How do you handle data integrity in a MongoDB cluster?
10. Explain aggregation pipelines in MongoDB. Provide an example use case.

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Advanced MongoDB Questions

1. How does MongoDB scale horizontally?
2. What is auto-sharding, and how does it work in MongoDB?
3. Explain write concerns in MongoDB and how they affect performance and consistency.
4. What is read concern in MongoDB, and how does it affect data consistency?
5. What are the different consistency levels in MongoDB, and how do they impact performance?
6. How does replica set failover work in MongoDB?
7. What is Oplog in MongoDB, and how is it used in replication?
8. What is the difference between MongoDB and other NoSQL databases like Cassandra or Redis?
9. Explain data modeling best practices in MongoDB.
10. What is Capped Collection in MongoDB? How does it differ from regular collections?

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Performance Optimization

1. How do you optimize query performance in MongoDB?
2. Explain indexing strategies in MongoDB.
3. What is covered index in MongoDB, and how does it help with performance?
4. How do you monitor MongoDB performance and troubleshoot performance bottlenecks?
5. What is the purpose of Aggregation Framework, and how can it be optimized?
6. How would you optimize a slow query in MongoDB?
7. What are the best practices for indexing in MongoDB?
8. What is write heavy vs read heavy workload, and how does it affect MongoDB performance?
9. How do you denormalize data in MongoDB for better performance?
10. How would you ensure data consistency in distributed MongoDB setups?

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Data Security and Authentication

1. How does MongoDB authentication work?
2. What are the different authentication mechanisms available in MongoDB?
3. What is role-based access control (RBAC) in MongoDB, and how does it work?
4. How do you encrypt data at rest in MongoDB?
5. How do you handle data access permissions in MongoDB for different users?
6. What is SSL/TLS encryption in MongoDB, and why is it important?
7. Explain field-level encryption in MongoDB.
8. What is audit logging, and how can it be enabled in MongoDB?
9. How does MongoDB handle backups, and what are the best practices for backup and recovery?
10. What are the security considerations when deploying MongoDB in the cloud?

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Real-World Scenarios

1. How would you migrate data from relational databases to MongoDB?
2. Explain a scenario where you had to optimize MongoDB for handling large datasets.
3. How would you set up a high availability system using MongoDB?
4. How do you handle multi-region deployments in MongoDB for global applications?
5. Describe how you would design a social media application using MongoDB.
6. How do you handle real-time data updates in MongoDB?
7. How would you design a blogging platform with MongoDB?
8. What are some common pitfalls you should avoid while working with MongoDB?
9. How would you handle data replication in a multi-cloud environment with MongoDB?
10. How would you implement geo-spatial queries in MongoDB?

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Sharding and Scaling

1. How does sharding work in MongoDB? What are the benefits?
2. What are the types of sharding keys in MongoDB, and how do you choose the best one?
3. How would you troubleshoot shard key issues in MongoDB?
4. What is the role of the mongos process in a sharded cluster?
5. How does chunk splitting work in MongoDB when sharding data?
6. How does MongoDB manage large datasets in sharded clusters?
7. Explain the balancing process in MongoDB's sharded architecture.
8. What are the limitations of sharding in MongoDB?
9. How would you handle migrations in a sharded MongoDB setup?
10. What are zone sharding and its use case in MongoDB?

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Backup and Restore

1. How do you backup a MongoDB instance?
2. Explain how point-in-time restores work in MongoDB.
3. How would you restore a MongoDB backup to a different server?
4. How does replication help with backup and restore in MongoDB?
5. What is MongoDB Ops Manager, and how can it be used for backup management?
6. What are the best practices for disaster recovery in MongoDB?
7. How do you back up sharded clusters in MongoDB?
8. How does WiredTiger storage engine affect backup and restore?
9. How do you ensure consistent backups when using MongoDB replication?
10. How do you restore a MongoDB database in case of data corruption?

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Version Upgrades and Migration

1. How do you handle version upgrades in MongoDB without downtime?
2. What are the new features introduced in the latest MongoDB versions?
3. How do you migrate from MongoDB 3.x to MongoDB 4.x?
4. How would you perform a rolling upgrade in a MongoDB cluster?
5. What is the MongoDB Atlas service, and how does it differ from self-managed MongoDB deployments?
6. How do you decommission old nodes in a MongoDB replica set or sharded cluster?
7. How do you handle data migration between different MongoDB versions?
8. How does MongoDB's WiredTiger storage engine impact performance in later versions?
9. What are the compatibility considerations when upgrading MongoDB versions?
10. How do you ensure backward compatibility with MongoDB in long-term projects?

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Miscellaneous MongoDB Questions

1. What is MongoDB Atlas, and what are its benefits over self-hosted MongoDB?
2. How do you enable logging in MongoDB?
3. How does MongoDB handle large object storage (BLOBs)?
4. What are MongoDB drivers, and how do you interact with MongoDB from different programming languages?
5. What is MongoDB Stitch, and how does it simplify backend development?
6. How would you configure MongoDB replication with specific read and write concerns for your app?
7. How does MongoDB handle deadlocks in a multi-threaded environment?
8. What is the difference between MongoDB Atlas and self-hosted MongoDB in terms of scaling and management?
9. How does MongoDB compare to other NoSQL databases like Cassandra and Couchbase?
10. What strategies would you implement to handle large-scale MongoDB data migration?