Since you seem to be concerned only about whether "found" equals either "hit" or "miss", try this:
index=app (splunk_server_group=bex OR splunk_server_group=default) sourcetype=rpm-web* host=rpm-web* "CACHE_NAME=RATE_SHOPPER" method=GET found IN("hit","miss")
| stats count by found
from User warren – Stack Overflow https://stackoverflow.com/questions/71836567/how-to-make-pie-chart-of-these-values-in-splunk/71844522#71844522
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