# PRD

## 1. Overview

**Purpose**: Simple User Settings provides basic user preferences storage and retrieval. It allows users to persist key-value configuration data at the user level.

**Target Users**:
- **Platform Developers** — store user preferences for applications
- **External API Consumers** — manage user settings via REST API

**Key Problems Solved**:
- **Settings persistence**: reliable storage for user preferences
- **Tenant isolation**: user settings scoped to tenant context
- **Simple API**: easy-to-use key-value interface

**Success Criteria**:
- Settings operations < 100ms P99
- Data consistency and durability

**Capabilities**:
- Store user settings as key-value pairs
- Retrieve user settings by key
- Update existing settings
- Delete user settings

## 2. Actors

### 2.1 Human Actors

#### End User

**ID**: `fdd-user-settings-actor-end-user`

<!-- fdd-id-content -->
**Role**: Platform user who stores and retrieves personal preferences and configuration data.
<!-- fdd-id-content -->

### 2.2 System Actors

#### Consumer Application

**ID**: `fdd-user-settings-actor-consumer`

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**Role**: Application gear that stores/retrieves user settings on behalf of end users.
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## 3. Use Cases

### Store User Settings

**ID**: [ ] `p1` `fdd-user-settings-usecase-store-v1`

<!-- fdd-id-content -->
User stores preference data (JSON format) associated with their account. System saves settings scoped to user and tenant.

**Actors**: `fdd-user-settings-actor-end-user`, `fdd-user-settings-actor-consumer`
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### Retrieve User Settings

**ID**: [ ] `p1` `fdd-user-settings-usecase-retrieve-v1`

<!-- fdd-id-content -->
User or application retrieves stored settings by key or all settings. System returns data scoped to user and tenant.

**Actors**: `fdd-user-settings-actor-end-user`, `fdd-user-settings-actor-consumer`
<!-- fdd-id-content -->

### Update User Settings

**ID**: [ ] `p1` `fdd-user-settings-usecase-update-v1`

<!-- fdd-id-content -->
User or application modifies existing settings. System merges updates with existing data.

**Actors**: `fdd-user-settings-actor-end-user`, `fdd-user-settings-actor-consumer`
<!-- fdd-id-content -->

## 4. Functional Requirements

### Settings Storage

**ID**: [ ] `p1` `fdd-user-settings-fr-storage-v1`

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System SHALL store settings as JSON key-value pairs, support nested JSON objects, with tenant-scoped storage.

**Actors**: `fdd-user-settings-actor-consumer`
<!-- fdd-id-content -->

### Settings Retrieval

**ID**: [ ] `p1` `fdd-user-settings-fr-retrieval-v1`

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System SHALL retrieve all settings for a user, retrieve specific setting by key, and return default values for missing settings.

**Actors**: `fdd-user-settings-actor-consumer`
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### Settings Management

**ID**: [ ] `p1` `fdd-user-settings-fr-management-v1`

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System SHALL support updating existing settings, deleting settings by key, and merging updates with existing settings.

**Actors**: `fdd-user-settings-actor-consumer`
<!-- fdd-id-content -->

## 5. Non-Functional Requirements

### Response Time

**ID**: [ ] `p1` `fdd-user-settings-nfr-response-time-v1`

<!-- fdd-id-content -->
System SHALL respond in < 100ms P99 for reads and < 200ms P99 for writes.
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### Tenant Isolation

**ID**: [ ] `p1` `fdd-user-settings-nfr-tenant-isolation-v1`

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System SHALL ensure settings are strictly scoped to tenant with no cross-tenant access and user authentication required.
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### Data Consistency

**ID**: [ ] `p1` `fdd-user-settings-nfr-consistency-v1`

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System SHALL provide ACID guarantees for writes with no partial updates.
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## 6. Out of Scope

- Settings versioning/history
- Settings sharing between users
- Complex query capabilities
- Settings validation schemas

## Appendix

### Change Log

| Date | Version | Author | Changes |
|------|---------|--------|---------|
| 2026-02-09 | 0.1.0 | System | Initial PRD for cypilot validation |
