The thesis Development of an application based on hexagonal architecture and Domain-Driven Design focuses on elaborating and analyzing key concepts and principles of Domain-Driven Design and their implementation through hexagonal software development architecture. The first part of the paper is grounded in the theoretical description of Domain-Driven Design concepts and Hexagonal Architecture, also known as "Ports and Adapters" and "Clean" architecture. The thesis discusses the essence and significance of creating modular applications through the precise separation of public abstractions and implementation details, by isolating domain logic from infrastructure and utilized technologies. Additionally, the thesis also emphasizes the importance of logically segregating code into modules, communication via APIs, and the subsequent decoupling of application components. This is noted for its impact on the capabilities for code testing, the introduction of new features, and the upgrading or replacement of existing technologies and business functionalities, as well as the potential for transforming modules into individual microservices.The aim of the paper is to address key concepts of Domain-Driven Design and hexagonal architecture and to consider the importance of encapsulation, abstraction, and protection of business logic from the rest of the system as their primary tenets. The theoretical part of the paper allows for the identification of the advantages of hexagonal architecture over monolithic, single-module software architecture, as well as potential challenges in its implementation and maintenance.