Couch DB Interview Questions & Answers

CouchDB Basics:

1. What is CouchDB?

   • CouchDB is a NoSQL database that uses JSON for documents, JavaScript for queries, and HTTP for an API.

2. Explain the key features of CouchDB.

   • Schema-free JSON documents
   • MapReduce views for querying
   • Multi-Version Concurrency Control (MVCC)
   • Replication for distributed databases

3. How is data stored in CouchDB?

   • Data is stored as JSON documents, which are organized into databases.

4. What is the purpose of the _id field in CouchDB documents?

   • The _id field uniquely identifies a document within a database.

5. How does CouchDB handle conflicts in a distributed environment?

   • CouchDB uses Multi-Version Concurrency Control (MVCC) to handle conflicts. Each update creates a new version, and conflicts are resolved during replication.

CouchDB Querying:

6. What is a MapReduce function in CouchDB?

   • A MapReduce function is used to create views in CouchDB. The map function extracts data, and the reduce function aggregates it.

7. Explain the difference between a map function and a reduce function.

   • The map function extracts data and emits key-value pairs, while the reduce function aggregates the values for a given key.

8. How can you query CouchDB?

   • CouchDB uses MapReduce views for querying. Views are defined using map and optional reduce functions.

9. What is the purpose of the reduce function in CouchDB views?

   • The reduce function is used to aggregate and summarize the data emitted by the map function.

CouchDB Administration:

10. How do you create a new database in CouchDB?

    • You can create a new database using the HTTP PUT request to the CouchDB server.

11. Explain the process of replicating databases in CouchDB.

    • Replication in CouchDB involves copying changes from one database to another, ensuring consistency between databases.

12. What is the CouchDB _all_docs endpoint used for?

    • The _all_docs endpoint retrieves all documents in a database.

13. How can you secure a CouchDB instance?

    • CouchDB can be secured using authentication, authorization, and SSL encryption.

CouchDB Design Documents:

14. What is a design document in CouchDB?

    • A design document is a special type of document that contains views, indexes, and other metadata.

15. How do you create a design document in CouchDB?

    • Design documents are created by inserting a document with a specific _id format, typically starting with "_design/".

CouchDB Replication:

16. Explain the purpose of CouchDB replication.

    • Replication is used to synchronize data between two or more CouchDB databases, providing fault tolerance and scalability.

17. What is continuous replication in CouchDB?

    • Continuous replication ensures that changes are continually replicated in real-time as they occur.

CouchDB Security:

18. How can you implement user authentication in CouchDB?

    • CouchDB supports various authentication methods, including basic authentication and OAuth.

19. Explain the role of the _security object in CouchDB.

    • The _security object is used to define access control lists (ACLs) for databases.

20. What is SSL and how is it used in CouchDB?

    • SSL (Secure Sockets Layer) is used to encrypt communication between CouchDB and clients, enhancing security.

CouchDB Views Optimization:

21. How can you optimize a CouchDB view for better performance?

    • Use the include_docs option judiciously, limit the number of emitted keys, and consider using the reduce function efficiently.

22. Explain the purpose of the startkey and endkey parameters in CouchDB views.

    • startkey and endkey parameters define a range for querying view results.

Miscellaneous CouchDB Questions:

23. What is Fauxton in CouchDB?

    • Fauxton is the web-based administration interface for CouchDB.

24. How does CouchDB handle backups?

    • CouchDB provides a backup utility called couchdb-dump to create a backup of a database.

25. What is the role of the _rev field in CouchDB documents?

    • The _rev field (revision) keeps track of changes to a document and is used for conflict resolution.

26. Explain the use of the CouchDB _changes feed.

    • The _changes feed provides a continuous stream of changes happening in a database.

27. What are the advantages of using CouchDB over traditional relational databases?

    • CouchDB offers schema flexibility, horizontal scalability, and seamless replication, making it suitable for distributed and decentralized systems.

28. How does CouchDB handle indexing?

    • CouchDB uses B-tree indexing for fast access to documents and views.

29. What is the purpose of the CouchDB Futon tool?

    • Futon is a web-based interface for CouchDB that allows users to interact with databases.

30. Explain the concept of eventual consistency in CouchDB.

    • CouchDB provides eventual consistency, meaning that changes are eventually propagated to all nodes in a distributed system.