Database of ORS

I looked in the documentation and here on the forum, but I didn’t find anything that answered my question. I would like to know which database is used by the ORS to store the data generated from the OSM_FILE

ORS does not use a database but stores the data in its own format in files on disc. With the default configuration this data is located in a folder ‘graphs’ containing a sub-folder for each of the routing profiles. The exact format is not documented (besides the actual source code) as it is subject to change with each feature that requires new data. If you wish to get more insight into the details, the only way is unfortunately to study the FlagEncoder-classes of ORS and the EncodedValue-classes of the corresponding Graphhopper-fork.