What is MongoDB? List main features.
MongoDB is a popular NoSQL database designed for modern applications. Unlike traditional relational databases, MongoDB stores data in flexible, JSON-like documents rather than tables. This makes it ideal for handling unstructured or semi-structured data while offering scalability, high performance, and ease of use.
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Flexible Schema: Supports schema-less design, letting you adapt to changing requirements without rigid constraints.
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High Scalability: Horizontal scaling is achieved through sharding, where data is distributed across multiple servers.
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Replication: Provides redundancy and high availability through replica sets, ensuring data is consistently replicated across nodes.
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Indexing: Supports various index types to optimize query performance, including single field, compound, and text indexes
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Geospatial Queries: Enables queries for geolocation data, making it useful for applications requiring maps or location-based features.
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Rich Query Language: Includes powerful query capabilities, such as filtering, sorting, aggregations, and joins using the operator.
Scenario Questions
0-2 years experience
- 1If you need to store user profiles with varying fields, how would you model them in MongoDB?
- 2What happens if you try to insert a document that exceeds the 16 MB BSON size limit?
- 3How would you retrieve all orders placed in the last 24 hours using a MongoDB query?
2-5 years experience
- 1Your team notices read latency spikes after adding a new index. How would you investigate and decide whether to keep the index?
- 2We have a microservice that writes logs to MongoDB, but the collection is growing rapidly. What strategies would you use to manage storage and maintain performance?
- 3During a deployment, a write operation fails with a duplicate key error. How would you debug the cause and prevent it in the future?
5-8 years experience
- 1Design a high‑availability architecture for a globally distributed e‑commerce platform using MongoDB. Discuss replication, sharding, and read/write concerns.
- 2Our application experiences occasional write conflicts under heavy load. How would you configure MongoDB to ensure ACID guarantees while minimizing performance impact?
- 3Explain how you would migrate a legacy relational database to MongoDB, handling data transformation and consistency.
8+ years experience
- 1At a large enterprise, you need to decide whether to adopt MongoDB for a new analytics pipeline that requires complex joins. What factors would influence your decision, and how would you mitigate MongoDB’s limitations?
- 2How would you set up a multi‑region, multi‑cloud deployment of MongoDB to satisfy strict latency SLAs and disaster‑recovery requirements?
- 3Discuss the long‑term operational considerations—schema evolution, data governance, backup strategy—when standardizing MongoDB across several product teams.
Follow-up Questions
- Can you compare MongoDB’s transaction model to that of a traditional RDBMS?
- What are the main trade‑offs when choosing between embedding and referencing documents?
- How does MongoDB’s sharding key selection impact query performance?