Does the first log.info output line include the quotes? i.e.
signatureKey : "abc"
or is it:
signatureKey : abc
?
(i.e. Could it be that the second needs to be "\"abc\"".equalsIgnoreCase(signatureKey) ?)
More specifically: If the document stored already includes the quotes, the RawStringTranscoder will not do anything to remove/interpret the quotes and you have to deal with them as part of the result. The default behaviour will interpret/handle the quotes and allow you to retrieve just their content.
(Ref: https://docs.couchbase.com/java-sdk/current/howtos/transcoders-nonjson.html#rawstringtranscoder )