How to have data consistency in H2 database after scaling up the spring boot application

I have a spring boot application which connects to in memory H2 database. If I have to horizontally scale up the spring boot application with say 2-3 parallel instances ( I am using docker ). How can we achieve data consistency between the H2 database of each instance. Such that even if the request goes to any instance the data in all the 3 instances of H2 database is always in synch.