Systems Decomposition

Before implementing, let’s properly decompose this feature:

Context

1. What are we building? Describe the feature.
2. Who triggers it? User action, system event, scheduled?
3. What should happen? The happy path outcome.

Data Flow Mapping

Map the complete flow:

[Trigger] → [Input] → [Validation] → [Business Logic] → [Side Effects] → [Output]

For each step:

• What data comes in?
• What transformation happens?
• What data goes out?
• What can go wrong?

Interface Contracts

Define explicit interfaces:

Input Schema

• What fields are required?
• What are the types and constraints?
• Validation rules?

Output Schema

• Success response format?
• Error response format?
• All possible error types?

Error Enumeration

List ALL possible errors:

• Validation errors
• Not found errors
• Authorization errors
• External service errors
• System errors

Boundaries

Clarify ownership:

• What does this component OWN?
• What does it NOT own?
• What are the integration points?

Dependencies

For each external dependency:

• What is it?
• Sync or async?
• What if it fails?
• How do we recover?

This decomposition will guide implementation.