System Design Document (SDD) is the outcome of the third phase developed by the software design professionals. SDD describes the new system intention or replacement design, with the detailed descriptions of the system architecture and its related components. Some firms develop two levels of SDD, namely, High Level Design (HLD) and Low Level Design (LLD) documents. Our use case's SDD is built with the mobile application architecture along with a few internal component designs. Typically, the detail design document covers the input format, database design, processing logic, output layouts, operating environment, interface specifications, and so on.