Simply generate some read and write SQL queries to a database cluster (mariadb in my case).

sqltraffic.bash

#!/bin/bash

## manual section
#
# options
# --rqmax   Define the max read queries
# --rqpm    Define read queries per minute
# --wqmax   Define the max wirte queries 
# --wqpm    Define write queries per minute
# 
# keep in mind: the read and write queries are additive
#
# usage
# ./sqltraffic.bash --rqmax 10000 --rqpm 60 --wqmax 600 --wqpm 10
#

## config section 
# hosts to query
HOSTS=( 192.168.178.121 192.168.178.122 192.168.178.123 192.168.178.124 \
    192.168.178.125 192.168.178.126 192.168.178.127 )

# mysql client opts 
MYOPTS="-BN -u root -ppassword"

# define read query
RQ="SELECT id FROM X.t1 ORDER BY id DESC LIMIT 1;"

# define write query
WQ="INSERT INTO D.t1 (id, data) VALUES (' ' , 'foo' );"

# define a log file for reconstruction
LOG="output.log"

## runtime section
# parse options
until [ "$1" == "" ]; do
    case $1 in
        --rqmax ) shift ; Q=$1 ;;
        --rqpm ) shift ; D=$1 ;;
        --wqmax ) shift ; W=$1 ;;
        --wqpm ) shift ; P=$1 ;;
        * ) shift ; shift ;; # shift ALL the things!
    esac
    shift
done

N=${#HOSTS[@]}

function readqueries () {
    local CR=0
    local SLEEP=$(echo "60 $D" | awk '{printf "%f", $1 / $2}')
    until [ $CR -ge $Q ]; do
        H=${HOSTS[$((RANDOM % N))]}
        mysql $MYOPTS -h $H -e "$RQ" &>/dev/null
        echo "R $H $(date --rfc-3339=ns ) $CR"
        sleep $SLEEP
        ((CR++))
    done
    echo "FIN at $CR"
}

function writequeries () {
    local CW=0
    local SLEEP=$(echo "60 $P" | awk '{printf "%f", $1 / $2}')
    until [ $CW -ge $W ]; do
        H=${HOSTS[$((RANDOM % N))]}
        mysql $MYOPTS -h $H -e "$WQ" &>/dev/null
        echo "W $H $(date --rfc-3339=ns ) $CW"
        sleep $SLEEP
        ((CW++))
    done
    echo "FIN at $CW"
}

# lets have some fun
echo > $LOG
(readqueries >> $LOG ) &
(writequeries >> $LOG ) &