How to parse a variable in while loop multiple times - bash

Question

Here is my shell script and where 'i' stands for key.txt. Key file consists of around 8 properties and its values separated by a space like shown below.
Key.txt file :
bat slservice
solr slservice
tvs kimservice
ACM kimservice
product kimservice
tax kimservice
tvs kimservice
SNB taxservice
Shell script:
#!/bin/bash
while read i
do
key=$(echo $i | awk '{print $1}')
service=`echo $i | awk '{print $2}'`
ip=`cat IP.txt | grep $service | awk '{print $2}'|awk 'NR==1{print $1}'`
echo "VALIDATING $service properties"
echo "validating $key in $service IP = $ip"
curl -X GET -H "Content-type: application/json" -H "Accept: application/json" http://${ip}/v1/config 2>/dev/null>$service.json
v1_value=$(jq ".\"$key\"" "$service.json" | grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b")
echo "$key $v1_value" > file.txt
acutal_value=$(cat file.txt | grep "$key" | awk '{print $2}')
LB_name=$(cat mapping.txt | grep "$key" | awk '{print $2}')
LB_ip=$(cat LB.txt | grep "${LB_name}" | awk '{print $2}')
if [ "${acutal_value}" == "${LB_ip}" ]; then
echo "$key of $service value is matching $v1_value = $LB_ip"
else
echo "$key of $service v1/value ${acutal_value} is notmatching to GCP LB ${LB_ip}"
fi
done < key.txt
The above script is working fine and giving the exact output if we use mapping.txt file alone as a input file for LB_name variable.
But in my current situation I have 4 mapping (mapping1.txt to mapping4.txt)files and each mapping file should run only once for execution of all the props in key file and then followed by 2,3,4 files.
Here is the exact line that we are talking about:
LB_name=$(cat mapping.txt | grep "$key" | awk '{print $2}')
Waiting for suggestions !