What does the design phase include?

The design phase in the SDLC begins after requirements have been gathered and approved. Its goal is to translate "what needs to be done" into "how it will work". At this step the architecture, data structure, interfaces, and technical decisions that will define all further development are formed.

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#Core idea

Design is the creation of a system plan, an analog of a blueprint for a house. If at the analysis stage we found out which rooms are needed, now we decide how to route the walls, wiring, and utilities so the house is reliable and convenient. Mistakes here are especially costly: a wrong architecture later drags out a rewrite of half the product.

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#Main components of the design phase

1. Architectural design (High-Level Design) The overall structure of the system is defined: modules, their connections, integration points, interaction with external services. It is decided which type of architecture fits - monolith, microservices, client-server, REST API, and so on. At this level the technologies are also chosen (programming language, database, frameworks).
2. Detailed design (Low-Level Design) Each module is described in detail: classes, functions, interfaces, data structures, algorithms. Diagrams are created (for example, UML), interaction scenarios and possible exceptions are described. This is where the specifics developers rely on when writing code appear.
3. Database design It is defined which data will be stored, how tables are related, which keys and indexes are needed. The result is ER diagrams (Entity-Relationship) showing the data structure and relationships between entities.
4. Interface and UX/UI design For user-facing systems, screen logic, navigation, and element interaction are worked out. Mockups, prototypes, and user action scenarios are created. The goal is to make the product intuitive and clear before development.
5. Security and infrastructure design Ways of authorization, encryption, and data protection are worked out. It is defined how the system will be deployed, scaled, and updated (DevOps aspects). This often includes choosing cloud solutions, containerization, logging, and monitoring.

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#Results of the design phase

• an architectural diagram of the system;
• technical documentation (technical specification, module specs, ER diagrams, UML diagrams);
• interface prototypes;
• a list of tools and technologies for implementation.

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#Conclusion

The design phase turns a set of requirements into a clear technical model of the future product. The quality of this phase determines how easily the team will be able to implement, test, and maintain the system in the future.