CASSANDRA Skills 3

Question 1

What does a Cassandra consistency level of QUORUM mean for a cluster with a replication factor of 3?

Accepted Answer

At least 2 replicas must acknowledge

Answer

QUORUM requires a majority, calculated as floor(RF/2) + 1, so for RF=3 that means 2 acknowledgments.

Question 2

Which tool can you use to profile slow CQL queries in a Cassandra 4.x cluster?

Accepted Answer

TRACING ON in cqlsh

Answer

Enabling `TRACING ON` in cqlsh produces a detailed, per-stage execution trace for each query including coordinator and replica activity.

Question 3

In Cassandra, what is a 'wide partition' and why is it a potential problem?

Accepted Answer

A partition with many rows that can cause memory pressure and slow reads

Answer

Wide partitions can grow unboundedly and cause GC pressure, coordinator timeouts, and OOM errors during compaction.

Question 4

What is the role of the commit log in Apache Cassandra?

Accepted Answer

Provides durability by recording writes before they hit the memtable

Answer

The commit log is an append-only, durable write-ahead log that ensures no data is lost if a node crashes before its memtable is flushed.

Question 5

When should you use a Cassandra Materialized View instead of a denormalized table?

Accepted Answer

When you need Cassandra to automatically maintain a read-optimized copy of a base table

Answer

Materialized Views are automatically updated by Cassandra when the base table changes, eliminating the need for application-level dual writes.

CASSANDRA - Apache Cassandra Database Practice Test