title: Query is slow - large result
body: <p>This table:</p>
  <pre><code>CREATE TABLE buckets (
      year_month text,
      source_id uuid,
      nano_since_epoch bigint,
      max double,
      min double,
      num_values int,
      sum double,
      value double,
      PRIMARY KEY ((year_month, source_id), nano_since_epoch)
  )
  </code></pre>
  <p>and this query:</p>
  <pre><code>select value from buckets where year_month = '2020_9' AND source_id=699ddcc0-5896-4b35-a901-8eec2f221499
  </code></pre>
  <p>It works, but the  query takes ~4 sec. to complete. Result set has ~48.000 rows.
  Cluster has 3 nodes running on GCP, n1-standard-2 (2 vCPUs, 7.5 GB memory).
  Not using SSDs. Almost same performance on the second DC with only 1 node, on a much larger -bare metal- machine.</p>
  <p>Table histograms:</p>
  <pre><code>Percentile  SSTables     Write Latency      Read Latency    Partition Size        Cell Count
                                (micros)          (micros)           (bytes)                  
  50%             0.00             51.01             73.46            182785             17084
  75%             0.00             61.21            182.79           1629722            126934
  95%             3.00            182.79            654.95           4055269            315852
  98%             3.00            263.21            785.94           4866323            454826
  99%             4.00            315.85            943.13           5839588            454826
  Min             0.00              4.77             20.50                43                 0
  Max             4.00           2816.16            943.13           5839588            454826
  </code></pre>
  <p>Is it possible to speed up fetching of the results or is the size of the result the limiting factor here?</p>
  <p><strong>EDIT:</strong>
  Cassandra is running in docker on the VMS. Memory utilization on the VM is ~ 50%</p>
  <p>Dockerfile:</p>
  <pre><code>services:
      elassandra:
          image: strapdata/elassandra:6.2.3.23
          container_name: elassandra
          environment:
              - CASSANDRA_BROADCAST_ADDRESS=10.164.0.58
              - CASSANDRA_SEEDS=10.164.0.58
              - CASSANDRA_CLUSTER_NAME=Prod Cluster 2
              - CASSANDRA_NUM_TOKENS=256
              - CASSANDRA_DC=datacenter-prod
              - CASSANDRA_RACK=rack1
              - LOCAL_JMX=no
          volumes:
              - '/opt/elassandra/data:/opt/elassandra/data'
              - '/var/log/cassandra:/var/log/cassandra'
              - '/var/lib/cassandra:/var/lib/cassandra'
          ports:
              - 7000:7000
              - 7001:7001
              - 7199:7199
              - 8080:8080
              - 8081:8081
              - 9042:9042
              - 9160:9160
              - 9200:9200
              - 9300:9300
          ulimits:
              memlock: -1
              nproc: 32768
              nofile: 100000
          network_mode: &quot;host&quot;
          logging:
              driver: syslog
              options:
                tag: cassandra-0
  </code></pre>