Cassandra settings tuning for CAS updates - cassandra

Question

What are the settings to consider for lightweight transactions( Compare and Set) in Cassandra–2.1.8?
a. We are using token aware load balancing policy with a LeveledCompactionStrategy setting on the table. Table has skinny rows with a single column in the primary key. We use prepared statements for all the queries and are prepared once and cached.
b. The below are the settings,
i. Max Heap – 4G, New Heap – 1G, 4 Core CPU, CentOS
ii. Connection pool is based on the concurrency settings for the test.
final PoolingOptions pools = new PoolingOptions();
pools.setNewConnectionThreshold(HostDistance.LOCAL, concurrency);
pools.setCoreConnectionsPerHost(HostDistance.LOCAL, maxConnections);
pools.setMaxConnectionsPerHost(HostDistance.LOCAL, maxConnections);
pools.setCoreConnectionsPerHost(HostDistance.REMOTE, maxConnections);
pools.setMaxConnectionsPerHost(HostDistance.REMOTE, maxConnections);
iii. protocol version – V3
iv. Set tcp delay to true to disable Nagle’s algorithm. (default)
v. Compression is enabled.
2. Throughput increases with concurrency on a single connection. For CAS RW, the throughput does scale at same rate as Simple RW.
100000 requests, 1 thread Simple RW CAS RW
Mean rate (ops/sec) 643 265.4
Mean latency (ms) 1.554 3.765
Median latency (ms) 1.332 2.996
75th percentile latency (ms) 1.515 3.809
95th percentile latency (ms) 2.458 8.121
99th percentile latency (ms) 5.038 11.52
Standard latency deviation 0.992 2.139
100000 requests, 25 threads Simple RW CAS RW
Mean rate (ops/sec) 7686 1881
Mean latency (ms) 3.25 13.29
Median latency (ms) 2.695 12.203
75th percentile latency (ms) 3.669 14.389
95th percentile latency (ms) 6.378 20.139
99th percentile latency (ms) 11.59 61.973
Standard latency deviation 3.065 6.492

Answer 1

The most important consideration for speed on LWT is partition contention. If you have several updates on a single partition, it will be slower. Beyond that, you are looking at machine performance tuning.
There is a free, full course here to help with that: https://academy.datastax.com/courses/ds210-operations-and-performance-tuning