CASSANDRA Architecture and Data Model

Question 1

What is the primary data distribution mechanism in Apache Cassandra?

Accepted Answer

Consistent hashing with a token ring

Answer

Cassandra uses consistent hashing on a token ring to distribute data evenly across nodes without a central coordinator.

Question 2

Which component in Cassandra is responsible for in-memory writes before they are flushed to disk?

Accepted Answer

MemTable

Answer

A MemTable is an in-memory write-back cache that accumulates mutations before being flushed to an immutable SSTable on disk.

Question 3

What does the term 'eventual consistency' mean in the context of Cassandra?

Accepted Answer

All replicas will converge to the same value given no new updates

Answer

Eventual consistency guarantees that if no new updates are made, all replicas will eventually return the same value.

Question 4

In Cassandra's data model, what is a 'partition key' used for?

Accepted Answer

Determining which node stores the data

Answer

The partition key is hashed to a token that determines which node(s) are responsible for storing that partition.

Question 5

What is the purpose of a Bloom filter in Cassandra?

Accepted Answer

Quickly determine if an SSTable may contain a given partition key

Answer

A Bloom filter is a probabilistic data structure that lets Cassandra skip reading SSTables that definitely do not contain the requested key.

CASSANDRA - Apache Cassandra Database Practice Test