A Technical Design Document (TDD) includes information about the programmatic approach of how a particular requirement will be implemented. 

TDDs are prepared primarily by the technical solution architect or technical lead for the final development. They are also used by the testing team to write detailed test cases. The following are the key objectives of technical design documentation:

• The details of feature architecture and design goals
• Solution and data validation
• Documentation of the code (high-level)
• Process and data flow diagrams