documentation-and-adrs

Documentation and ADRs

Overview

Document decisions, not just code. The most valuable documentation captures the why — the context, constraints, and trade-offs that led to a decision. Code shows what was built; documentation explains why it was built this way and what alternatives were considered. This context is essential for future humans and agents working in the codebase.

When to Use

• Making a significant architectural decision
• Choosing between competing approaches
• Adding or changing a public API
• Shipping a feature that changes user-facing behavior
• Onboarding new team members (or agents) to the project
• When you find yourself explaining the same thing repeatedly

When NOT to use: Don't document obvious code. Don't add comments that restate what the code already says. Don't write docs for throwaway prototypes.

Architecture Decision Records (ADRs)

ADRs capture the reasoning behind significant technical decisions. They're the highest-value documentation you can write.

When to Write an ADR

• Choosing a framework, library, or major dependency
• Designing a data model or database schema
• Selecting an authentication strategy
• Deciding on an API architecture (REST vs. GraphQL vs. tRPC)
• Choosing between build tools, hosting platforms, or infrastructure
• Any decision that would be expensive to reverse

ADR Template

Store ADRs in docs/decisions/ with sequential numbering:

# ADR-001: Use PostgreSQL for primary database

## Status

Accepted | Superseded by ADR-XXX | Deprecated

## Date

2025-01-15

## Context

We need a primary database for the task management application. Key requirements:

- Relational data model (users, tasks, teams with relationships)
- ACID transactions for task state changes
- Support for full-text search on task content
- Managed hosting available (for small team, limited ops capacity)

## Decision

Use PostgreSQL with Prisma ORM.

## Alternatives Considered

### MongoDB

- Pros: Flexible schema, easy to start with
- Cons: Our data is inherently relational; would need to manage relationships manually
- Rejected: Relational data in a document store leads to complex joins or data duplication

### SQLite

- Pros: Zero configuration, embedded, fast for reads
- Cons: Limited concurrent write support, no managed hosting for production
- Rejected: Not suitable for multi-user web application in production

### MySQL

- Pros: Mature, widely supported
- Cons: PostgreSQL has better JSON support, full-text search, and ecosystem tooling
- Rejected: PostgreSQL is the better fit for our feature requirements

## Consequences

- Prisma provides type-safe database access and migration management
- We can use PostgreSQL's full-text search instead of adding Elasticsearch
- Team needs PostgreSQL knowledge (standard skill, low risk)
- Hosting on managed service (Supabase, Neon, or RDS)