Architecture Decision Records (ADR)

Expert assistance for creating and maintaining Architecture Decision Records in Confluence.

When to Use This Skill

• Documenting architectural decisions

• Recording technology choices

• Explaining design decisions

• Creating technical decision logs

• User mentions: ADR, architecture, technical decision, design choice

What Are ADRs?

Architecture Decision Records document important architectural decisions made during a project:

Purpose

• Record context: Why the decision was needed

• Document options: What alternatives were considered

• Explain choice: Why this option was selected

• Note consequences: What are the trade-offs

Benefits

• Historical record of decisions

• Onboarding new team members

• Preventing decision revisitation

• Understanding system evolution

• Avoiding repeated mistakes

ADR Structure

Standard Template (Michael Nygard format)

[Number]. [Title]

Date: YYYY-MM-DD Status: [Proposed | Accepted | Deprecated | Superseded] Decision Makers: [Names or team] Technical Story: [Optional ticket/issue reference]

Context

What is the issue we're seeing that is motivating this decision or change?

Decision

What is the change that we're proposing and/or doing?

Consequences

What becomes easier or more difficult to do because of this change?

Positive

• List of positive consequences

Negative

• List of negative consequences
• Known limitations
• Trade-offs

Example ADR

001. Use PostgreSQL for Primary Database

Date: 2024-01-15 Status: Accepted Decision Makers: Engineering Team Technical Story: PROJ-123

Context

We need to select a database system for our new user management service. The service will:

• Handle up to 1M users initially, growing to 10M
• Require complex queries across multiple tables
• Need ACID compliance for user transactions
• Support full-text search on user profiles
• Integrate with our existing infrastructure

We evaluated several options:

• PostgreSQL
• MySQL
• MongoDB
• DynamoDB

Decision

We will use PostgreSQL 15 as our primary database.

Key factors in this decision:

1. ACID Compliance: Strong guarantees for user data integrity
2. Complex Queries: Excellent support for JOINs and aggregations
3. JSON Support: Native JSONB for flexible schema evolution
4. Full-Text Search: Built-in search capabilities with tsvector
5. Proven at Scale: Used successfully by similar applications
6. Team Expertise: Team has 5+ years PostgreSQL experience
7. Cost: Open source with commercial support available

Consequences

Positive

• Data Integrity: ACID compliance ensures user data consistency
• Query Flexibility: Rich SQL support for complex reporting
• Future-Proof: JSON support allows schema evolution
• Performance: Excellent performance for our workload patterns
• Ecosystem: Vast ecosystem of tools and extensions
• Monitoring: Mature monitoring and debugging tools
• Team Velocity: Team can be productive immediately

Negative

• Scaling Complexity: Horizontal scaling requires additional tooling (Citus)
• Operational Overhead: Requires database administration expertise
• Backup Strategy: Need to implement robust backup/recovery
• Cloud Lock-in: Managed PostgreSQL ties us to cloud provider
• Migration Cost: Future migration to different database would be expensive

Mitigation Strategies

• Use connection pooling (PgBouncer) for connection management
• Implement read replicas for read scaling
• Regular backup testing and disaster recovery drills
• Database versioning with migration tools (Flyway)
• Monitor query performance with pg_stat_statements

Alternatives Considered

MySQL:

• ✅ Similar performance and features
• ❌ Less sophisticated JSON support
• ❌ Team less experienced

MongoDB:

• ✅ Excellent horizontal scaling
• ❌ No ACID transactions (at the time)
• ❌ Weak JOIN support for complex queries

DynamoDB:

• ✅ Fully managed, auto-scaling
• ❌ Complex query limitations
• ❌ Higher cost at scale
• ❌ AWS lock-in

Notes

This decision can be revisited if:

• Scale exceeds 50M users
• Query patterns change dramatically
• Team expertise shifts
• Cost becomes prohibitive

References

• PostgreSQL Documentation
• Benchmark Results
• Cost Analysis Spreadsheet

ADR Statuses

Proposed

• Decision is under discussion

• Not yet implemented

• Open for feedback

Accepted

• Decision has been approved

• Implementation in progress or complete

• Current recommendation

Deprecated

• Decision is no longer recommended

• Still in use but should be phased out

• Usually replaced by a newer ADR

Superseded

• Decision has been replaced

• Reference the new ADR

• Kept for historical context

Rejected

• Decision was considered but not adopted

• Explains why it was rejected

• Prevents revisiting

Types of ADRs

Technology Selection

005. Use React for Frontend Framework

Context

Need to select frontend framework for new dashboard application.

Requirements:

• Rich interactive UI
• Real-time updates
• Mobile responsive
• Large community support
• Component reusability

Decision

Selected React 18 with TypeScript.

Consequences

[...]

Architecture Pattern

008. Adopt Microservices Architecture

Context

Monolithic application becoming difficult to maintain and deploy.

Challenges:

• Long deployment cycles
• Tight coupling
• Difficult to scale independently
• Team coordination overhead

Decision

Migrate to microservices architecture over 12 months.

Consequences

[...]

Security Decision

012. Implement OAuth 2.0 for Authentication

Context

Need secure, industry-standard authentication.

Requirements:

• Third-party login support
• Token-based authentication
• Refresh token rotation
• Security best practices

Decision

Implement OAuth 2.0 with PKCE flow.

Consequences

[...]

Infrastructure Choice

015. Deploy on AWS Using ECS Fargate

Context

Need container orchestration solution.

Options evaluated:

• Self-managed Kubernetes
• AWS ECS Fargate
• Google Cloud Run
• Heroku

Decision

Use AWS ECS Fargate for container deployment.

Consequences

[...]

ADR Best Practices

1. Write When Decision Is Made

• Document as decisions happen

• Don't wait until later

• Capture context while fresh

2. Be Specific and Concrete

• Avoid vague language

• Include concrete examples

• Reference metrics and data

3. Acknowledge Trade-offs

• Every decision has trade-offs

• Be honest about limitations

• Don't oversell the solution

4. Link Related ADRs

• Reference superseded ADRs

• Note related decisions

• Show decision evolution

5. Keep It Concise

• Focus on key points

• Link to detailed analysis

• 1-2 pages maximum

6. Use Consistent Format

• Same structure for all ADRs

• Predictable organization

• Easy to scan

7. Number Sequentially

• 001, 002, 003, etc.

• Never reuse numbers

• Gaps are OK (rejected ADRs)

ADR Workflow

1. Identify Decision Needed

Team realizes: "We need to decide on a caching strategy"

2. Research Options

Options:

• Redis
• Memcached
• In-memory (application)
• CDN caching

3. Draft ADR

Create ADR with:

• Context and requirements
• Options evaluated
• Recommendation
• Trade-offs

4. Review and Discuss

Team reviews:

• Technical lead approval
• Security review if needed
• Architecture team input

5. Accept and Implement

• Mark as "Accepted"
• Publish to Confluence
• Implement the decision
• Link from related docs

6. Maintain Over Time

• Update if context changes
• Deprecate if superseded
• Add learnings and updates

Confluence Organization

ADR Structure in Confluence

Architecture Space ├── ADR Index (list of all ADRs) ├── ADR Template └── Decision Records/ ├── 001-use-postgresql-for-database.md ├── 002-adopt-microservices-architecture.md ├── 003-implement-oauth-authentication.md ├── 004-use-redis-for-caching.md └── ...

ADR Index Page

Architecture Decision Records

Active Decisions

Deprecated Decisions

Rejected Proposals

Categories

Infrastructure

• ADR-001: Database Selection
• ADR-015: Container Orchestration

Frontend

• ADR-005: Frontend Framework
• ADR-009: State Management

Backend

• ADR-012: Authentication Method
• ADR-014: API Design

Security

• ADR-012: OAuth 2.0 Authentication
• ADR-016: Encryption at Rest

Templates for Different Decision Types

Technology Selection Template

[Number]. Select [Technology Type] for [Purpose]

Date: YYYY-MM-DD Status: Proposed Decision Makers: [Team]

Context

Requirements

• List functional requirements
• List non-functional requirements
• List constraints

Evaluation Criteria

1. Criterion 1 (weight: X%)
2. Criterion 2 (weight: Y%)
3. Criterion 3 (weight: Z%)

Options Evaluated

Option 1: [Technology A]

Pros:

• Pro 1
• Pro 2

Cons:

• Con 1
• Con 2

Score: X/10

Option 2: [Technology B]

[Same structure]

Option 3: [Technology C]

[Same structure]

Decision

Selected [Technology X] because [brief reasoning].

Consequences

Implementation Impact

• What changes are needed
• What stays the same

Performance Impact

• Expected performance characteristics
• Benchmarks if available

Cost Impact

• Initial costs
• Ongoing costs
• Hidden costs

Team Impact

• Training needed
• Learning curve
• Hiring implications

Risk Assessment

Process Change Template

[Number]. Adopt [Process/Practice]

Date: YYYY-MM-DD Status: Proposed Decision Makers: [Team]

Context

Current State

• How things work now
• Pain points
• Metrics showing problems

Desired State

• What we want to achieve
• Success metrics
• Expected benefits

Decision

Adopt [Process/Practice] with the following approach:

1. Step 1
2. Step 2
3. Step 3

Consequences

Team Changes

• New roles or responsibilities
• Required training
• Schedule impacts

Tooling Changes

• New tools needed
• Integration requirements
• Costs

Rollout Plan

• Phase 1: Pilot (dates)
• Phase 2: Expansion (dates)
• Phase 3: Full adoption (dates)

Success Metrics

• Metric 1: Target value
• Metric 2: Target value
• Metric 3: Target value

Updating ADRs

When to Update

DO update when:

• Adding lessons learned

• Noting implementation challenges

• Recording actual vs expected consequences

• Adding references or links

DON'T update when:

• Decision needs to change → Create new ADR

• Context has changed significantly → Create new ADR

• Original reasoning was wrong → Create new ADR with Supersedes

Update Format

Add updates section at the end:

Updates

2024-03-15: Performance Issues Discovered

After 3 months in production, we discovered that [issue]. We've mitigated this by [solution]. Consider ADR-XXX for future improvements.

2024-06-20: Cost Higher Than Expected

Actual monthly cost is $X vs expected $Y because [reason]. Updated cost estimates in budget.

How I'll Help

When creating ADRs, I will:

Identify the decision:

• What needs to be decided?

• Why is it important?

• Who should be involved?

Research context:

• Read related code

• Review existing docs

• Find similar decisions

Structure the ADR:

• Use appropriate template

• Fill in all sections

• Add relevant details

Evaluate options:

• List alternatives

• Analyze trade-offs

• Provide recommendations

Create in Confluence:

• Format as ADF

• Add to ADR index

• Link related documents

Maintain over time:

• Add updates

• Track status changes

• Deprecate when superseded

Example Interaction

You: "We just decided to use Redis for caching. Can you create an ADR?"

Me: "I'll create an ADR for the Redis caching decision.

Let me gather some information:

• What were you using before?

• What other options did you consider?

• What were the key factors in choosing Redis?

• Any concerns or trade-offs?

[You provide context]

I'll create ADR-004: Use Redis for Application Caching

Draft:

• Context: Need caching to reduce database load (currently 1000 QPS)

• Evaluated: Redis, Memcached, in-memory caching

• Decision: Redis for persistence, pub/sub, and rich data types

• Consequences: Positive (performance, flexibility), Negative (ops overhead, cost)

Should I create this in Confluence? Which space?"

You: "Yes, space 456789"

Me: [Creates ADR page] "Created ADR-004 in space 456789! Link: https://your-domain.atlassian.net/wiki/spaces/456789/pages/...

Also updating the ADR Index to include this new decision."