Sometimes, for extremely simple uses, when I don't want the hassle of selecting a Docker container that has jq, I'll just use a Python oneliner so I don't have to learn extra syntax, can use Python's list comprehensions, etc:

  <<< '{"a":"b", "c":"d"}' python3 -c 'import json,sys;print(json.loads(sys.stdin.read())["c"])'

This also works with a Python script with more lines if I need to add complexity or readability, or any feature, API calls, etc.