First 4 usecases complete with optimized code. Replace case holds cronological order of database files at the cost of time (delete then add would be faster). No dedicated folder or files for databses, database files can be stored system wide. SHDB auto installs to /usr/local/bin/db thus is included in PATH. SHDB does not create database files, developers must touch files then pass that file as db_file parameter.
tested on freebsd, debian and kali.