There is a demand for a way to get the EPSG authority code for an unidentified CRS. "Unidentified" means a CRS without identifiers. In Well Known Text (WKT) terms, this means a CRS without AUTHORITY[...] element.
One possible approach is to scan over the full EPSG database, instantiate every CRS and compare them with the unidentified CRS until a match is found. The comparaison is done with CRS.equalsIgnoreMetadata(...). However this approach is slow and consume a lot of resources. For some factory like the SQL-backed EPSG factory, it is possible to reduce the set of CRS to instantiate.
This request for enhancement is about defining an API for CRS lookup which provides a opportunity for optimisation in some authority factories like the EPSG one.