JQ examples

.servers[] | select(.role == "backend") | .ip

.countries | sort_by(.population) | reverse | .[] | .name

.calls | group_by(.route) | map({key: .[0].route, value: map(.path)})

.calls | group_by(.route) | map({key: .[0].route, value: map(.callTimeMs) | length})

.calls | group_by(.route) | map({key: .[0].route, value: map(.callTimeMs) | add})

to_entries

.countries[] | [{key:.name, value: {id, population}}] | from_entries

with_entries(.key |= ("0"+.))

.countries | map({name, id, people: .population})

map_values({name, ageYears: .age})

def isLocalhost: . == "127.0.0.1";

.hosts[] | {localhost: .host | isLocalhost}

def areaFromCountry: if . == "USA" then "North America"
  elif . == "Germany" then "Europe"
  elif . == "Japan" then "Asia"
  else "Unknown"
  end;

.countries[] | {area: .name | areaFromCountry}