Java project, 3 web and 2 web communication, how to keep one-to-one correspondence?

3 external web application servers
2 Service servers
customers access 3 external servers (one domain name corresponds to 3), and then three peer-to-peer web queries data from 2 Service servers. How to ensure that when 2 Service servers return messages to 3 external web, they will return to the correct server?

Feb.14,2022
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3e0e4-4096d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3e0e4-4096d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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