How to find an item in a json array using kusto

you could use mv-expand or mv-apply:

print d = dynamic([
  {
    "Key": "key0",
    "Value": 0
  },
  {
    "Key": "key1",
    "Value": 2
  }
])
| mv-apply d on (
    where d.Key == "key0"
    | project d.Value 

) 

from: https://stackoverflow.com/questions/59370390/how-to-find-an-item-in-a-json-array-using-kusto