CrateDB performance

hey,engineer,I have some question need your help in running CrateDB
Question 1: /crate.2.6/bin/crate.in.sh set the heap memory to 2G,
but in the background process, Java running memory reaches 1.9g, is it normal?
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Question 2: whether frequent insertion and modification of data will slow down the efficiency of crateDB database query。