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Architecture Decision Records (ADRs)¤

This directory contains Architecture Decision Records (ADRs) for the AI Chat system. ADRs document significant architectural decisions that affect the system's structure, behavior, or non-functional characteristics.

What is an ADR?¤

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

  • Document the reasoning behind architectural choices
  • Preserve institutional knowledge when team members change
  • Facilitate onboarding of new team members
  • Enable informed changes by understanding past decisions
  • Avoid repeating past mistakes or discussions

ADR Process¤

When to Write an ADR¤

Create an ADR when making decisions about:

  • Technology choices (frameworks, libraries, databases)
  • Architectural patterns (microservices vs monolith, event-driven architecture)
  • System boundaries and service interfaces
  • Data storage strategies and schemas
  • Security and compliance approaches
  • Performance and scalability strategies
  • Development practices that affect architecture

ADR Lifecycle¤

graph LR
    A[Proposed] --> B[Accepted]
    B --> C[Superseded]
    B --> D[Deprecated]
    A --> E[Rejected]

    classDef proposed fill:#fff2cc
    classDef accepted fill:#d5e8d4
    classDef superseded fill:#f8cecc
    classDef deprecated fill:#ffe6cc
    classDef rejected fill:#f8cecc

    class A proposed
    class B accepted
    class C superseded
    class D deprecated
    class E rejected

Status Definitions:

  • Proposed: The ADR is under consideration
  • Accepted: The ADR is approved and the decision is implemented
  • Superseded: A new ADR has replaced this decision
  • Deprecated: The decision is no longer recommended but may still be in use
  • Rejected: The proposal was considered but not adopted

ADR Template¤

Use the ADR template when creating new ADRs:

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# ADR-NNNN: [Short Title]

**Date:** YYYY-MM-DD  
**Status:** [Proposed | Accepted | Superseded | Deprecated | Rejected]  
**Supersedes:** [List of ADR numbers this supersedes, if any]  
**Superseded by:** [ADR number that supersedes this, if any]

## Context and Problem Statement

[Describe the context and problem statement that led to this decision]

## Decision Drivers

- [Driver 1]
- [Driver 2]
- [Driver N]

## Considered Options

- [Option 1]
- [Option 2]
- [Option N]

## Decision Outcome

**Chosen option:** [Option X]

**Reasoning:** [Explanation of why this option was chosen]

### Consequences

**Positive:**
- [Consequence 1]
- [Consequence 2]

**Negative:**
- [Consequence 1]
- [Consequence 2]

**Neutral:**
- [Consequence 1]
- [Consequence 2]

## Implementation Notes

[Any specific implementation guidance, constraints, or considerations]

## Related Decisions

- [Link to related ADRs]
- [References to external documentation]

Current ADRs¤

Note: ADR files are created as architectural decisions are made. The following represent planned ADRs that will document key system decisions:

Infrastructure and Deployment¤

  • ADR-0001: Multi-Agent Architecture - Decision to implement specialized agents for different conversation types
  • ADR-0002: Message Queue System - Selection of Redis-based message queue for asynchronous processing
  • ADR-0003: Observability Stack - OpenTelemetry + Jaeger + Prometheus + Grafana for monitoring

Data and Storage¤

  • ADR-0004: Database Strategy - PostgreSQL for primary data storage with Redis for caching
  • ADR-0005: Validation Pipeline - Real-time response validation and quality scoring

Development and Operations¤

  • ADR-0006: Development Framework - Node.js + TypeScript + React Native technology stack
  • ADR-0007: Container Strategy - Docker + Docker Compose for development and deployment
  • ADR-0008: Testing Strategy - Multi-layered testing approach with unit, integration, and E2E tests

Creating a New ADR¤

Step 1: Determine ADR Number¤

Find the next available ADR number by checking existing files:

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ls docs/architecture/decisions/ | grep -E '^[0-9]{4}' | sort -n | tail -1

Step 2: Copy Template¤

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# Copy the template
cp docs/_templates/adr-template.md docs/architecture/decisions/NNNN-short-title.md

# Edit the new file
$EDITOR docs/architecture/decisions/NNNN-short-title.md

Step 3: Fill Out Content¤

  1. Replace placeholder text with actual content
  2. Set the status to "Proposed" initially
  3. Describe the context and problem thoroughly
  4. List all considered options with pros/cons
  5. Document the decision and reasoning
  6. Identify consequences (positive, negative, neutral)

Step 4: Review Process¤

  1. Create a pull request with the new ADR
  2. Tag relevant stakeholders for review
  3. Discuss in team meetings if needed
  4. Iterate based on feedback
  5. Change status to "Accepted" when approved
  6. Merge the pull request

Step 5: Update Index¤

Add the new ADR to this README.md file in the appropriate section.

ADR Best Practices¤

Writing Guidelines¤

  • Be concise but complete - Include all necessary context without unnecessary detail
  • Use clear language - Avoid jargon and explain technical terms
  • Include diagrams when they help explain the decision
  • Link to relevant resources and documentation
  • Update status as decisions evolve
  • Cross-reference related ADRs

Content Guidelines¤

  • Focus on "why" not just "what" - Explain the reasoning behind decisions
  • Document alternatives that were considered and why they were rejected
  • Be honest about trade-offs - Every decision has consequences
  • Include implementation notes for complex decisions
  • Specify success criteria when applicable

Maintenance Guidelines¤

  • Review ADRs regularly - Ensure they're still relevant and accurate
  • Update status when decisions change
  • Create superseding ADRs instead of editing old ones
  • Archive obsolete ADRs rather than deleting them
  • Keep the index updated with new ADRs

Tools and Automation¤

ADR Management Scripts¤

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# Create a new ADR (future enhancement)
./scripts/new-adr.sh "Multi-tenant Architecture"

# List all ADRs with status
./scripts/list-adrs.sh

# Update ADR status
./scripts/update-adr-status.sh 0001 "Superseded"

# Generate ADR index
./scripts/generate-adr-index.sh

Integration with Development Workflow¤

  • Link ADRs in code comments when implementing decisions
  • Reference ADRs in pull requests that relate to architectural changes
  • Include ADR reviews in architecture review meetings
  • Update project documentation to reference relevant ADRs

Examples and Templates¤

Decision Context Examples¤

Technology Selection: 

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We need to choose a message queue solution that can handle high throughput 
with reliable delivery guarantees for our AI chat system.

Architectural Pattern: 

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The system is growing and we need to decide between maintaining a monolith 
or splitting into microservices to improve scalability and team autonomy.

Data Strategy: 

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User conversations are growing rapidly and we need to decide on a storage 
strategy that balances query performance with cost efficiency.

Decision Outcome Examples¤

Clear Decision: 

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We will use Redis as our message queue because it provides the best balance 
of performance, reliability, and operational simplicity for our current scale.

Decision with Timeline: 

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We will migrate to microservices over 6 months, starting with the authentication 
service to minimize risk while gaining operational experience.

Conditional Decision: 

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We will use PostgreSQL for transactional data and implement read replicas 
if read performance becomes a bottleneck (measured by >200ms p95 latency).

Resources¤

ADR Tools and References¤

Best Practices Resources¤