Architecture Decision Records (ADRs)¶

Purpose: Document all significant architectural decisions with context, alternatives, and rationale
Audience: CTO, Technical Team, Investors, Auditors
Owner: CTO / Solution Architect
Last Updated: 2025-12-26
Status: Active

What is an ADR?¶

An Architecture Decision Record (ADR) is a document that captures an important architecture decision made along with its context and consequences.

Why ADRs Matter:

• ✅ Institutional Memory: Preserve the "why" behind decisions
• ✅ Onboarding: Help new team members understand rationale
• ✅ Audit Trail: Show investors/auditors thoughtful decision-making
• ✅ Future Reference: Understand trade-offs when revisiting decisions
• ✅ Avoid Repetition: Don't re-debate settled questions

ADR Process¶

When to Create an ADR¶

Create an ADR for any decision that:

• Affects system structure or architecture
• Has long-term impact (hard to reverse)
• Involves significant trade-offs
• Costs substantial money or time
• Affects security, performance, or scalability
• Involves vendor selection

Examples:

• ✅ Choosing a database (Cosmos DB vs. MongoDB Atlas)
• ✅ Selecting an LLM provider (OpenAI vs. Anthropic)
• ✅ Microservices vs. Monolith
• ✅ Cloud provider selection
• ❌ Adding a new utility function (too small)
• ❌ Changing CSS colors (not architectural)

ADR Template¶

# ADR-XXX: [Decision Title]

**Status:** [Proposed | Accepted | Deprecated | Superseded]  
**Date:** YYYY-MM-DD  
**Decision Makers:** [Names/Roles]  
**Consulted:** [Stakeholders consulted]  
**Informed:** [Who was informed]

---

## Context

What is the issue we're addressing? What are the constraints?

## Decision

What decision did we make?

## Alternatives Considered

1. **Alternative 1**
   - Pros: ...
   - Cons: ...
2. **Alternative 2**
   - Pros: ...
   - Cons: ...

## Consequences

**Positive:**

- Benefit 1
- Benefit 2

**Negative:**

- Trade-off 1
- Trade-off 2

**Neutral:**

- Thing we'll need to monitor

## Compliance & Security

How does this decision affect compliance (GDPR, DPDPA) and security?

## Migration Path

If we need to reverse this decision later, how would we do it?

## Related ADRs

- Links to related decisions

---

**Last Updated:** YYYY-MM-DD  
**Review Date:** [When to reassess this decision]

ADR Workflow¶

flowchart LR
    A[Identify Decision Needed] --> B[Research Alternatives]
    B --> C[Create ADR Draft]
    C --> D[Team Review]
    D --> E{Consensus?}
    E -->|No| B
    E -->|Yes| F[CTO Approval]
    F --> G[Merge ADR]
    G --> H[Communicate Decision]
    H --> I[Implement]

    style A fill:#E3F2FD
    style F fill:#FFF3E0
    style I fill:#E8F5E9

MachineAvatars ADRs¶

Index of All ADRs¶

ADR Categories¶

Infrastructure Decisions¶

• ADR-002: Cosmos DB
• ADR-003: Milvus
• ADR-006: Azure Cloud

AI/ML Decisions¶

• ADR-001: LLM Selection
• ADR-009: Embedding Model (planned)
• ADR-010: TTS Provider (planned)

Architecture Patterns¶

• ADR-004: Microservices
• ADR-011: API Gateway Pattern (planned)

Frontend Decisions¶

• ADR-005: Next.js
• ADR-012: 3D Library (Three.js) (planned)

Integration Decisions¶

• ADR-007: Authentication
• ADR-008: Payment Provider

ADR Governance¶

Review Cycle¶

All ADRs should be reviewed:

• Quarterly: For active decisions
• On major incidents: If decision contributed to issue
• Before major refactoring: To understand original rationale

Deprecation Process¶

If an ADR becomes obsolete:

1. Update status to "Deprecated"
2. Create new ADR with status "Supersedes ADR-XXX"
3. Link both ADRs
4. Explain why original decision no longer applies

Example:

# ADR-013: New Payment Provider (Stripe)

**Status:** Accepted (Supersedes ADR-008)  
**Date:** 2025-06-01

## Context

ADR-008 selected Razorpay for payments. However, due to [reasons],
we're migrating to Stripe.

## Migration from ADR-008

- Timeline: Q3 2025
- Dual-run period: June-July 2025
- Razorpay sunset: August 2025

Best Practices¶

Do's¶

✅ Be concise: 1-3 pages maximum
✅ Use clear language: Avoid jargon when possible
✅ Quantify trade-offs: Use numbers (cost, performance, time)
✅ Include diagrams: Visual explanations help
✅ Link to evidence: Benchmarks, research, RFCs
✅ Update status: Keep ADRs current
✅ Cross-reference: Link related ADRs

Don'ts¶

❌ Don't write novels: Keep it focused
❌ Don't hide trade-offs: Be honest about negatives
❌ Don't skip alternatives: Show you considered options
❌ Don't leave status vague: Always update status
❌ Don't make decisions in isolation: Consult stakeholders
❌ Don't forget compliance: Always consider security/privacy

Success Metrics¶

Tools & Resources¶

ADR Tools:

• adr-tools - Command-line tool for managing ADRs
• log4brains - Web UI for ADRs

References:

• Michael Nygard's Blog - Original ADR concept
• ADR GitHub Organization - Templates and examples

Related Documentation¶

• AI/ML Architecture

• Product Architecture¶

Last Updated: 2025-12-26
Version: 1.0
Owner: CTO / Solution Architect
Review Cycle: Quarterly

"Every decision tells a story. Document it."