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The TAD – Technical Architecture Design is a technical design document that describes how a software system is implemented from an architectural and technological perspective.
If the architecture "says what exists," the TAD explains how it actually works.
The TAD translates high-level architectural decisions into a technical, concrete, and implementable description, providing developers, DevOps, and integration teams with a clear guide for building the system.
What is the TAD for
The TAD has several key objectives:
- Reduce ambiguity between architecture and implementation
- Align technical teams on choices, standards, and constraints
- Support development by providing operational guidance
- Facilitate maintenance and evolution of the system
- Serve as a technical reference for onboarding and audits
In practice, it is the document that answers the question:
“Ok, we’ve decided on this architecture… now how do we build it?”
What a TAD contains
A TAD typically includes:
1. Technical architectural view
- Application components and their responsibilities
- Architectural patterns adopted (e.g., layered, hexagonal, microservices)
- Dependencies between components
2. Technology stack
- Languages, frameworks, and libraries
- Databases and persistence systems
- Middleware, message brokers, API gateways
3. Detailed diagrams
- Component diagrams
- Sequence diagrams
- Deployment diagrams
- Integration flows
4. Non-functional aspects
- Security (authentication, authorization, encryption)
- Performance and scalability
- Logging, monitoring, and observability
- Error handling
5. Constraints and technical decisions
- Architectural trade-offs
- Technological limitations
- Main Architecture Decision Records (ADR)
How a TAD is created
Creating a TAD is an iterative and collaborative process:
- Start from the HLD
- The TAD doesn't come out of nowhere: it is a specialization of the HLD
- Analyze functional and non-functional requirements
- Performance, security, availability, compliance
- Define technological choices
- Not just “what to use,” but why
- Design flows and interactions
- How components communicate with each other
- Synchronous vs asynchronous, protocols, data formats
- Validate with teams
- Architects, developers, DevOps
- The TAD must be usable, not just correct
TAD Examples
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| TAD - Layer-based |
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| TAD - Package-based |
Difference between TAD and HLD
This is the central point.
HLD – High Level Design
- Macro vision
- Describes the architecture at a conceptual level
- Focuses on:
- Macro-components
- Main integrations
- General architectural choices
- Legible even by non-technical stakeholders
👉 Answers the question:
“What kind of system are we building?”
TAD – Technical Architecture Design
- Micro vision
- Dives into technical and implementation details
- Focuses on:
- Specific technologies
- Internal structure of components
- Flows, configurations, patterns
- Designed primarily for technical teams
👉 Answers the question:
“How do we build it, concretely?”
In summary
| Aspect | HLD | TAD |
|---|---|---|
| Level | High | Detailed |
| Focus | Conceptual architecture | Technical implementation |
| Target | Stakeholders + Tech teams | Tech teams |
| Technology | Abstract | Specific |
| Objective | Vision and consistency | Realization and guidance |
Conclusion
The TAD does not replace the HLD: it completes it.
A good HLD without a TAD risks remaining theoretical; a TAD without an HLD risks being inconsistent.
Together, they form the fundamental bridge between architectural idea and working software.
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