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

A mutable in-memory structure

Answer

A write-ahead log

Answer

A network protocol buffer

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

It indexes partitions for fast lookup

Answer

It merges SSTables during compaction

Answer

It caches frequently read rows

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 compression ratio of SSTables

Answer

The number of nodes in the cluster

Answer

The consistency level for reads

Question 4

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

Accepted Answer

TimeWindowCompactionStrategy (TWCS)

Answer

SizeTieredCompactionStrategy (STCS)

Answer

LeveledCompactionStrategy (LCS)

Answer

UnifiedCompactionStrategy (UCS)

Question 5

What is 'tombstone' in Cassandra?

Accepted Answer

A deletion marker stored in SSTables to represent deleted data

Answer

A marker written at node startup

Answer

A log entry for schema changes

Answer

A backup snapshot file

Question 6

What does 'vnodes' (virtual nodes) provide in Cassandra?

Accepted Answer

More even data distribution by assigning multiple token ranges per physical node

Answer

Isolated namespaces for keyspaces

Answer

Virtual replicas for read performance

Answer

Logical shards for multi-tenancy