I have a distributed Splunk deployment and need to index JSON data, 1 object per row. Objects are serialized using NewtonSoft.JSON .NET library. I already configured both INDEXED_EXTRACTIONS = json and KV_MODE = json for my custom source type in props.conf for deployment app of forwarders, indexers, and heads.
...and you most likely want to use KV_MODE and not indexed extractions. Remember that in case 9d KV_MODE, this has to go on the search head, not on the indexer. In case of indexed extractions, it has to go on the indexer, and maybe on the search head (not sure about that).