HLD: High Level Design consist of sub-system design to define. It target architect, Technical leads etc. - Solution Technical Overview - interfaces - primary classes - Database entities with - Assumptions
LLD: Lower level design consist of individual module/section design for the sub-system. It primarily extension of HLD. It targets core developers & covers following items: - All classes entities & interfaces - DB Model (Tables, column attributes, indexes, constraints) - Algorithms for methods used in classes - Logging implementation
I hope it helps!!