CASSANDRA Performance and Tuning 1

Question 1

What consistency level in Cassandra offers the lowest latency but the weakest consistency guarantee?

Accepted Answer

ONE

Answer

Consistency level ONE requires only a single replica to respond, giving the lowest latency but risking stale reads if another replica has a newer version.

Question 2

What is the formula for calculating quorum in a Cassandra cluster?

Accepted Answer

(replication_factor / 2) + 1

Answer

Quorum is calculated as floor(replication_factor / 2) + 1, ensuring a majority of replicas must agree before a read or write succeeds.

Question 3

What does 'speculative execution' do in Cassandra drivers?

Accepted Answer

Sends duplicate requests to multiple replicas and uses the fastest response to reduce tail latency

Answer

Speculative execution fires off the same query to an additional replica after a configurable delay, reducing tail latency by using the faster response.

Question 4

Which Cassandra compaction strategy minimizes read amplification and is best for mixed read/write workloads?

Accepted Answer

LeveledCompactionStrategy (LCS)

Answer

LCS maintains SSTables in levels with size limits, minimizing read amplification to roughly 1 SSTable per read at the cost of higher write I/O.

Question 5

What is the 'row cache' in Cassandra and when should it be used?

Accepted Answer

An in-JVM cache of entire partitions for tables with very few partitions and high read frequency

Answer

The row cache stores entire partition rows in off-heap memory and is only beneficial for tables with a small number of frequently accessed partitions.

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA Performance and Tuning 1