Architecture Decision Records for Startups: A Complete Guide

Here's what happens in most startups:

The founder argues with the CTO about a technical decision.

They debate for 30 minutes. Nobody writes anything down.

Two months later, a new developer asks: "Why did we choose this database?"

Nobody remembers the original reasoning. They argue again. They debate again.

Wasted time. Confused team. Inconsistent decisions.

Smart startups? They use Architecture Decision Records (ADRs).

This guide shows you what ADRs are, why they matter for startups, and how to write them in 5 minutes.

What Are Architecture Decision Records (ADRs)?

Let's start with clear definition.

Definition

Architecture Decision Record (ADR) is a document that describes a significant architectural decision, the context, alternatives considered, and the consequences.

Key Point: ADRs are about recording decisions, not about making them.

What ADRs Document

Context: What problem are we solving?
Decision: What did we choose?
Alternatives: What other options did we consider?
Consequences: What are the pros and cons of this decision?
Status: Is this proposal, accepted, superseded, or deprecated?

What ADRs Don't Document

Minor decisions (variable naming, code style)
Temporary decisions (will change in a week)
Personal preferences (no business or technical impact)

Why ADRs Matter for Startups

Founders think documentation is for big companies. Here's why it's wrong.

1. Save Time on Recurring Debates

Without ADRs:

"Why did we choose PostgreSQL?" → debate again → waste 30 minutes
"Should we use REST or GraphQL?" → debate again → waste 45 minutes
New developers ask same questions every week

With ADRs:

"Why PostgreSQL?" → Read ADR-001 → 2 minutes
"REST vs GraphQL?" → Read ADR-003 → 3 minutes
New developers get up to speed in hours, not weeks

2. Learn from Past Decisions

Without ADRs:

Repeat mistakes
Don't know why things were done certain way
Can't improve decision-making process

With ADRs:

See pattern of good vs bad decisions
Learn what worked and what didn't
Improve framework for future decisions

3. Onboard New Team Members Faster

Without ADRs:

New developer asks 50 questions in first week
Team explains same things repeatedly
Knowledge is in people's heads, not documentation

With ADRs:

New developer reads ADRs → understands system
Questions are deeper and more valuable
Team focuses on building, not explaining

4. Make Better Decisions

Without ADRs:

Decisions made in meetings without framework
Bias and politics influence choices
No way to review if decision was right

With ADRs:

Framework forces consideration of alternatives
Written reasoning reduces bias
Easy to review and learn from past decisions

ADR Template: Use This 5-Minute Format

Don't overcomplicate. Use this template.


markdown
# ADR-XXX: [Decision Title]

## Status

[Proposed | Accepted | Superseded by ADR-YYY | Deprecated]

## Context

[What problem are we solving? What constraints do we have?]
[What triggered this decision?]

## Decision

[What did we choose? Be specific and clear.]

## Alternatives Considered

### Option 1: [Alternative Name]

**Pros:**

- [Pro 1]
- [Pro 2]

**Cons:**

- [Con 1]
- [Con 2]

### Option 2: [Alternative Name]

**Pros:**

- [Pro 1]
- [Pro 2]

**Consequences**

- [Con 1]
- [Con 2]

### Option 3: [Alternative Name]

**Pros:**

- [Pro 1]
- [Pro 2]

**Cons:**

- [Con 1]
- [Con 2]

## Consequences of This Decision

### Positive Consequences

- [Good outcome 1]
- [Good outcome 2]

### Negative Consequences

- [Bad outcome 1]
- [Bad outcome 2]

### Risks and Mitigations

- [Risk 1] → [Mitigation strategy]
- [Risk 2] → [Mitigation strategy]

## Decision Date

[YYYY-MM-DD]

## Decision Makers

[Name 1, Name 2]

## Related ADRs

- [ADR-XXX: Related decision]
- [ADR-YYY: Related decision]

Real ADR Examples: Learn From These

Example 1: Database Selection


markdown
# ADR-001: Use PostgreSQL as Primary Database

## Status

Accepted

## Context

We're building MVP for B2B SaaS product. We need a relational database with:

- Strong consistency for financial transactions
- Good JSON support for flexible data
- Easy to find developers
- Mature ecosystem and tooling

Options considered: PostgreSQL, MySQL, MongoDB

## Decision

Use PostgreSQL as primary database.

## Alternatives Considered

### Option 1: PostgreSQL

**Pros:**

- Excellent JSON support with JSONB type
- Strong community and documentation
- Great developer availability for hiring
- Mature, battle-tested

**Cons:**

- Slower for simple read-heavy workloads

### Option 2: MySQL

**Pros:**

- Faster for read-heavy workloads
- Widely used

**Cons:**

- JSON support not as good as PostgreSQL
- Less developer enthusiasm for new hires

### Option 3: MongoDB

**Pros:**

- Flexible schema for rapid iteration
- Great for document-heavy applications

**Cons:**

- Weak consistency not suitable for transactions
- Harder to find experienced developers
- Schema flexibility can become technical debt

## Consequences of This Decision

### Positive Consequences

- Easy to hire PostgreSQL developers
- Strong consistency for financial data
- JSONB flexibility for evolving schema
- Mature ecosystem and tools (Prisma, pgAdmin, etc.)

### Negative Consequences

- Potential performance bottlenecks at very high scale
- May need to add Redis for caching read-heavy queries

### Risks and Mitigations

- **Risk:** Performance at scale → **Mitigation:** Add Redis caching for read-heavy queries, use read replicas if needed
- **Risk:** Schema changes become difficult → **Mitigation:** Use Prisma for migrations, design schema carefully

## Decision Date

2025-01-15

## Decision Makers

Alex (CTO), Sarah (Lead Developer)

## Related ADRs

- ADR-002: Use Prisma as ORM

Example 2: Frontend Framework


markdown
# ADR-003: Use Next.js for Frontend

## Status

Accepted

## Context

We're building web application that needs:

- Good SEO for marketing pages
- Fast development speed
- Easy to hire developers
- Performance at scale

Options considered: Next.js, Create React App (Vite), Remix

## Decision

Use Next.js (App Router) for frontend.

## Alternatives Considered

### Option 1: Next.js (App Router)

**Pros:**

- Built-in SEO with server-side rendering
- File-based routing is intuitive
- Strong community and documentation
- Easy to deploy to Vercel
- Server components reduce client bundle size

**Cons:**

- Learning curve for server components
- Some third-party libraries not optimized for Next.js

### Option 2: Create React App with Vite

**Pros:**

- Simple, no framework overhead
- Fastest development experience
- Maximum flexibility

**Cons:**

- SEO requires additional setup
- Need to add routing and state management manually
- No built-in optimization

### Option 3: Remix

**Pros:**

- Great performance
- Nested routes
- Built-in form handling

**Cons:**

- Smaller community than Next.js
- Harder to find developers
- Steeper learning curve for team

## Consequences of This Decision

### Positive Consequences

- SEO optimized from day one
- Fast development with built-in routing and optimizations
- Easy to hire Next.js developers
- Great performance with server components

### Negative Consequences

- Team needs to learn server components
- Some libraries need additional setup

### Risks and Mitigations

- **Risk:** Server components learning curve → **Mitigation:** Budget 1-2 weeks for team learning
- **Risk:** Third-party library compatibility → **Mitigation:** Choose libraries with Next.js support, use dynamic imports when needed

## Decision Date

2025-01-10

## Decision Makers

Alex (CTO), Mike (Frontend Lead)

## Related ADRs

- ADR-004: Use Supabase for Auth and Database Hosting

When to Write ADRs (Not Everything)

Don't document everything. That's as bad as documenting nothing.

Write ADRs For:

Significant Decisions (Do Document):

Tech stack choices (frameworks, databases, languages)
Architecture patterns (monolith vs microservices, serverless)
Third-party service selection (auth provider, payment processor, CDN)
Major refactoring or rewrites
API design decisions (REST vs GraphQL, versioning strategy)

Don't Write ADRs For:

Minor Decisions (Don't Document):

Variable naming conventions
Code style preferences
Minor library choices (e.g., date formatting library)
Temporary fixes or workarounds
Personal aesthetic preferences

Quick Decision Framework:

Ask yourself:

Will a new developer in 3 months need to know why we made this decision?
Will this decision impact system architecture for next 12+ months?
Would we spend >30 minutes re-debating this if someone asks?

If yes to any: Write ADR.

If no to all: Don't write ADR.

ADR Status Lifecycle: Track Evolution

Decisions change. ADRs should reflect that.

Status Types

1. Proposed

Decision is being discussed
Not yet finalized
ADR can be updated or rejected

2. Accepted

Decision is finalized
Implementation has started or completed
ADR won't change unless new information emerges

3. Superseded by ADR-YYY

Better decision was made
Old ADR is still valid for historical context
Link to new ADR that replaces it

4. Deprecated

Decision is no longer relevant
System or requirement changed
ADR kept for historical reference

Example of Superseded ADR:


markdown
# ADR-005: Use Express for Backend API

## Status

Superseded by ADR-012

## Context

[Original context...]

Add superseded note:


markdown
## Superseded By

This ADR was superseded by ADR-012 (Use tRPC for Backend API) on 2025-06-15.
Reason: We found tRPC provides better type safety and developer experience for our use case.

Where to Store ADRs: Keep Them Accessible

ADRs only work if team can find and read them.

Recommended Storage

Best: Version Control (Git)

Store in /docs/adr/ directory
Use numbered files (ADR-001-..., ADR-002-...)
Commit and review like code
Version history preserved automatically

Alternative:

Notion / Confluence (good for non-technical stakeholders)
Google Docs (simple, but lacks version control)
Dedicated ADR tool (overkill for most startups)

Directory Structure

/docs
  /adr
    /template.md
    /README.md (index of all ADRs)
    /001-use-postgresql-as-primary-database.md
    /002-use-prisma-as-orm.md
    /003-use-nextjs-for-frontend.md

ADR README (Index)

Create README.md in /docs/adr/ directory:


markdown
# Architecture Decision Records

This directory contains all ADRs for this project.

<div className="overflow-x-auto">
  <table className="min-w-full border-collapse border border-gray-300">
        <thead>
      <tr className="bg-gray-100">        <th className="border border-gray-300 px-4 py-3 text-left">
          ADR
        </th>
        <th className="border border-gray-300 px-4 py-3 text-left">
          Title
        </th>
        <th className="border border-gray-300 px-4 py-3 text-left">
          Status
        </th>
        <th className="border border-gray-300 px-4 py-3 text-left">
          Date
        </th>
      </tr>
    </thead>
    <tbody>
            <tr>
        <td class="px-4 py-3 text-sm text-gray-700 border-r border-gray-200 font-medium"><a href="./001-use-postgresql-as-primary-database.md">001</a></td>
        <td className="border border-gray-300 px-4 py-3">
          Use PostgreSQL as Primary Database
        </td>
        <td className="border border-gray-300 px-4 py-3">
          Accepted
        </td>
        <td className="border border-gray-300 px-4 py-3">
          2025-01-15
        </td>
      </tr>
      <tr>
        <td class="px-4 py-3 text-sm text-gray-700 border-r border-gray-200 font-medium"><a href="./002-use-prisma-as-orm.md">002</a></td>
        <td className="border border-gray-300 px-4 py-3">
          Use Prisma as ORM
        </td>
        <td className="border border-gray-300 px-4 py-3">
          Accepted
        </td>
        <td className="border border-gray-300 px-4 py-3">
          2025-01-10
        </td>
      </tr>
      <tr>
        <td class="px-4 py-3 text-sm text-gray-700 border-r border-gray-200 font-medium"><a href="./003-use-nextjs-for-frontend.md">003</a></td>
        <td className="border border-gray-300 px-4 py-3">
          Use Next.js for Frontend
        </td>
        <td className="border border-gray-300 px-4 py-3">
          Accepted
        </td>
        <td className="border border-gray-300 px-4 py-3">
          2025-01-10
        </td>
      </tr>

    </tbody>
  
  </table>
</div>

ADR Review Process: When to Revisit

Don't treat ADRs as permanent. Revisit when needed.

When to Review ADRs

Schedule Review (Every 6-12 Months):

Are decisions still valid?
Have constraints changed?
Are there better alternatives now?

Trigger Review (When Needed):

New team member questions validity
Performance or scalability issues emerge
Better technology or approach becomes available
Business requirements change significantly

Review Process

Read original ADR - understand context and reasoning
Assess current situation - has anything changed?
Consider new alternatives - are there better options now?
Decision: Keep as is, supersede with new ADR, or deprecate

Common ADR Mistakes

1. Writing ADRs After the Fact

Mistake: "We made decision last week, let's write ADR now."

Reality: You'll forget important context and alternatives.

Fix: Write ADRs before or during decision process, not after.

2. Making ADRs Too Long

Mistake: "Let's write 10-page document for every decision."

Reality: Nobody will read it. ADRs should be 5-10 minutes to read.

Fix: Keep ADRs concise. Link to external docs for details if needed.

3. Not Including Negative Consequences

Mistake: "We only need to document the good parts."

Reality: Understanding what won't work is as important as what will.

Fix: Always include negative consequences and risks. Hindsight bias kills learning.

4. Never Updating ADRs

Mistake: "We wrote ADR, done forever."

Reality: Technology and needs change. ADRs should reflect that.

Fix: Review ADRs every 6-12 months. Update or supersede when needed.

5. Writing ADRs Alone

Mistake: "CTO writes all ADRs."

Reality: ADRs should reflect team consensus, not one person's view.

Fix: Involve relevant team members in decision and documentation.

ADR Best Practices for Startups

1. Start Simple

Don't: Create complex ADR process, templates, and review boards.

Do: Use simple markdown template in Git. Start documenting.

2. Be Consistent

Don't: Write ADRs sometimes, skip other times.

Do: Document every significant decision. Make it habit.

3. Make Them Visible

Don't: Hide ADRs in obscure directory nobody checks.

Do: Link ADRs from main README. Mention them in onboarding.

4. Keep Them Alive

Don't: Write once, never review.

Do: Review and update ADRs regularly. Keep them relevant.

5. Learn From Them

Don't: Write ADRs, ignore them.

Do: Review past ADRs before making new decisions. Learn patterns.

Need Help with Technical Decisions?

At Startupbricks, we've helped startups make hundreds of architectural decisions. We know what to consider, what to avoid, and how to document decisions properly.

Whether you need:

Technical leadership and decision-making framework
ADR setup and team training
Architecture review and recommendations
Help with specific technical decisions

Let's talk about making better technical decisions.

Ready to document decisions? Download our free ADR Template and start today.

Architecture Decision Records for Startups: A Complete Guide

What Are Architecture Decision Records (ADRs)?

Definition

What ADRs Document

What ADRs Don't Document

Why ADRs Matter for Startups

1. Save Time on Recurring Debates

2. Learn from Past Decisions

3. Onboard New Team Members Faster

4. Make Better Decisions

ADR Template: Use This 5-Minute Format

Real ADR Examples: Learn From These

Example 1: Database Selection

Example 2: Frontend Framework

When to Write ADRs (Not Everything)

Write ADRs For:

Don't Write ADRs For:

Quick Decision Framework:

ADR Status Lifecycle: Track Evolution

Status Types

Example of Superseded ADR:

Where to Store ADRs: Keep Them Accessible

Recommended Storage

Directory Structure

ADR README (Index)

ADR Review Process: When to Revisit

When to Review ADRs

Review Process

Common ADR Mistakes

1. Writing ADRs After the Fact

2. Making ADRs Too Long

3. Not Including Negative Consequences

4. Never Updating ADRs

5. Writing ADRs Alone

ADR Best Practices for Startups

1. Start Simple

2. Be Consistent

3. Make Them Visible

4. Keep Them Alive

5. Learn From Them

Related Reading

Need Help with Technical Decisions?

Table of Contents