Can you explain the concept of DDD and its main principles?

DDD (Domain-Driven Design) is an approach to software development focused on a deep understanding of the subject area (domain) and close collaboration with domain experts.

Key principles of DDD:

• Focus on the domain and business logic. The entire architecture is built around the domain model.
• Ubiquitous Language. Developers and domain experts use a common language reflecting the domain terminology.
• Bounded Contexts. A large system is divided into separate parts with clearly defined boundaries and models.
• Modeling through entities, aggregates, services, and repositories.
• Isolation of infrastructure from domain logic.

Example: in an online store, entities are "Order," "User," "Product"; an aggregate is "Order" along with its items; services implement operations that do not belong to a specific entity, such as calculating delivery cost.