CouchDB Interview Questions and Answers for 10 years experience

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100 CouchDB Interview Questions & Answers (10+ Years Experience)

  1. What is CouchDB and how does it differ from traditional relational databases?

    • Answer: CouchDB is a NoSQL, document-oriented database. Unlike relational databases (like MySQL or PostgreSQL) which use tables and schemas, CouchDB stores data in JSON documents. This allows for flexible schema, meaning you don't need to define a rigid structure upfront. It's also highly scalable and distributed by design, making it suitable for large datasets and high availability needs. Key differences include data modeling (documents vs. tables), schema flexibility (schemaless vs. schema-defined), and query mechanisms (MapReduce vs. SQL).

  2. Explain the concept of a "document" in CouchDB.

    • Answer: In CouchDB, a document is a JSON object. It's a self-contained unit of data with key-value pairs. These keys are strings, and values can be various JSON data types (strings, numbers, booleans, arrays, nested objects). Each document has a unique ID, and revisions are tracked to maintain data integrity.

  3. What are views in CouchDB and how are they used?

    • Answer: Views are pre-defined queries that index data within your documents. They are defined using MapReduce functions. The map function processes each document and emits key-value pairs, and the reduce function aggregates these pairs. Views allow for efficient querying of data without scanning the entire database.

  4. Describe the MapReduce framework in CouchDB.

    • Answer: MapReduce is a programming model for processing large datasets. In CouchDB, the map function iterates through documents and emits key-value pairs based on your criteria. The reduce function then aggregates these emitted values based on the keys, performing summary operations like summing, counting, or averaging.

  5. How does CouchDB handle data replication?

    • Answer: CouchDB supports multi-master replication, meaning you can have multiple copies of your database synchronized across different servers. This provides high availability and fault tolerance. Changes made on one node are replicated to others, ensuring data consistency.

  6. What are some common use cases for CouchDB?

    • Answer: CouchDB is well-suited for applications requiring high scalability, availability, and flexibility. Common use cases include: real-time collaboration, mobile apps, logging systems, content management systems, and applications with high write loads.

  7. Explain the concept of revisions in CouchDB.

    • Answer: CouchDB tracks all changes to a document as revisions. Each update generates a new revision with a unique identifier. This allows for conflict resolution and data rollback, ensuring data integrity even in the face of concurrent updates.

  8. How does CouchDB handle conflicts?

    • Answer: When multiple updates to the same document occur concurrently from different sources and are not part of a defined replication process, CouchDB marks the document as a conflict. These conflicts must be manually resolved, potentially using revision history to determine the correct version.

  9. What are design documents in CouchDB?

    • Answer: Design documents contain views, lists, shows, and updates. These components provide the logic for querying and manipulating data within your database.

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