Kibana supports scripted fields, but they use Lucene Expressions, which does not operate on strings, so you'd have to index in the concatenated commandName and id during ingest (e.g. in Logstash).
As far as showing a stacked bar with Backend and DB, that should be possible using the Filters agg,
Only thing I'm not sure about is how you'd fit two bars that add up to more than 9.34 in a bar with max height of that magnitude, but maybe you need to use Kibana scripted fields to do additional calculations on the fields to end up to something that adds up.
