Combining many field as JSON and made it into a single field - PerformanceCombining many field as JSON and made it into a single field - Performance

I tried to combine multiple different fields (Stored Fields) into a JSON object and added in to lucene document as single field I get a better performance while reading the field from the index. though constructing the JSON requires additional time, It still retrieve the data faster What is the reason for this ?

I done update reading and indexing the data while reading I convert them back to single fields from JSON object