curl -s 10.0.0.145:8500/v1/kv/my_key/my_otehr_key/this_is_the_key?dc=dc1 | jq -r '.[0].Value' | base64 --decode
Same with python (instead of jq), available on all systems with scratch installation:
curl -s 10.0.0.145:8500/v1/kv/my_key/my_otehr_key/this_is_the_key?dc=dc1 | python -c 'import json,sys;obj=json.load(sys.stdin);print obj[0]["Value"];' | base64 --decode
or
curl -s 10.0.0.145:8500/v1/kv/my_key/my_otehr_key/this_is_the_key?raw