CASSANDRA Architecture and Data Model 2

Question 1

What is an SSTable in Apache Cassandra?

Accepted Answer

An immutable on-disk file that stores sorted partition data

Answer

SSTables (Sorted String Tables) are immutable, on-disk files written when a MemTable is flushed, containing sorted partition data.

Question 2

What role does the CommitLog play in Cassandra's write path?

Accepted Answer

It provides durability by recording every write before the MemTable

Answer

The CommitLog is written to first on every mutation to ensure durability in case of a node crash before the MemTable is flushed.

Question 3

What is the 'replication factor' in a Cassandra keyspace?

Accepted Answer

The number of copies of each partition stored across the cluster

Answer

The replication factor defines how many nodes store a replica of each partition, directly affecting fault tolerance.

Question 4

Which compaction strategy is best suited for time-series data that is mostly appended and rarely updated?

Accepted Answer

TimeWindowCompactionStrategy (TWCS)

Answer

TWCS groups SSTables into time windows and compacts within each window, making it ideal for time-series data with little or no overwrites.

Question 5

What is 'tombstone' in Cassandra?

Accepted Answer

A deletion marker stored in SSTables to represent deleted data

Answer

A tombstone is a deletion marker written to an SSTable that tells Cassandra to ignore older versions of that data during reads.

CASSANDRA - Apache Cassandra Database Practice Test