High Level Design documents are used for documenting, different modules and parts of the system and their relationships. So If you are documenting a Payment system, with the following parts:
Frontend Fraud system Banking Integration Module
A High Level Design document would talk about, what the Frontend is used for, how the Fraud System and Frontend communicated, What happens whenever fraud is detected in terms of a technical layman, How Frontend and Banking Integration System communicates and like.
Low Level Design Documents are, as the name implies lower level documents. They talk about inner workings of modules and describes which API's are chosen, which design is used for software development, which algorithms will be used. So they are mainly software implementation details.
For example, A Low Level Design for the example would talk about, which programming languages will be used for the Frontend (php/javascript/angular etc..), which design approach will be used (mvc,oop and like), which API endpoints are used between the Fraud system, or whether a hashing or a search tree algorithm will be used for blacklisting.
3.9k Views · View Upvotes