NoSQL Database Interview Questions

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What is the CAP theorem?

The CAP theorem: For a distributed system it is impossible to simultaneously provide more than two out of the three guarantees Consistency, Availability and Partition tolerance.

  • Consistency: It guarantees that every node in the distributed system returns the same, most successful, recent write.
  • Availability: When every request receives a response without the guarantee that it contains the most recent write.
  • Partition tolerance: When the system continues to function and upholds its guarantees in spite of network partitions.

When to use NoSQL Databases?

Following are some reasons for using a NoSQL database-

  • NoSQL data stores are distributed and are efficient in storing and handling huge volumes of data. Based on the targeted use cases, every NoSQL database has its data model for storing data.
  • NoSQL data stores provide scalability, i.e. additional storage can be easily created by simply adding nodes to the cluster.
  • Unlike RDBMS, NoSQL data stores are flexible and do not restrict themselves to a fixed schema. Hence, NoSQL data stores can adapt to changes in the schema of data Dynamically.

What are the NoSQL Databases?

NoSQL or "not only SQL," is an alternative to traditional relational databases where data is placed in tables and data schema is designed before the database is built. NoSQL databases are useful for working with large sets of distributed data. HBase is one such database. You can read more about it from the segments of the module “NoSQL Databases and Apache HBase”.