Technical Specification Template

Technical Specification Template

Technical specifications bridge the gap between high-level requirements and implementation. They provide enough detail for engineers to build features correctly while remaining flexible enough to adapt during development.

Why Use Technical Specifications?

Benefits:

• Aligns stakeholders on what will be built
• Reduces ambiguity during implementation
• Enables parallel work across teams
• Creates documentation for future reference
• Facilitates accurate estimation

When to write a tech spec:

• Features taking more than 1-2 weeks
• Cross-team projects
• Complex integrations
• User-facing features with specific requirements
• Performance-critical systems

The Template

# Technical Specification: [Feature Name]

**Version:** [1.0]
**Author:** [Name]
**Status:** [Draft | Review | Approved | In Development | Complete]
**Created:** [YYYY-MM-DD]
**Last Updated:** [YYYY-MM-DD]

## Overview

### Summary

[1-2 paragraph summary of the feature]

### Background

[Context and motivation for this feature]

### Goals

- [Primary goal 1]
- [Primary goal 2]

### Non-Goals

- [What this feature explicitly won't do]

## Requirements

### Functional Requirements

| ID | Requirement | Priority | Notes |
|----|-------------|----------|-------|
| FR-1 | [Requirement description] | [Must/Should/Could] | [Additional context] |
| FR-2 | [Requirement description] | [Must/Should/Could] | [Additional context] |

### Non-Functional Requirements

| ID | Category | Requirement | Target |
|----|----------|-------------|--------|
| NFR-1 | Performance | [Requirement] | [Metric] |
| NFR-2 | Security | [Requirement] | [Standard] |
| NFR-3 | Scalability | [Requirement] | [Target] |

### User Stories

**As a [user type], I want to [action] so that [benefit].**

#### Story 1: [Title]

**Acceptance Criteria:**
- [ ] Given [context], when [action], then [result]
- [ ] Given [context], when [action], then [result]

## Technical Design

### Architecture

[Architecture diagram or description]

┌─────────────┐ ┌─────────────┐ ┌─────────────┐ │ Client │────►│ Server │────►│ Database │ └─────────────┘ └─────────────┘ └─────────────┘

### Data Model

[Database schema changes]

```sql
CREATE TABLE [table_name] (
    id UUID PRIMARY KEY,
    [column] [type] [constraints],
    created_at TIMESTAMP DEFAULT NOW()
);

API Design

[API endpoints and contracts]

// POST /api/[endpoint]
interface CreateRequest {
  field1: string;
  field2: number;
}

interface CreateResponse {
  id: string;
  created_at: string;
}

Component Design

[Frontend/backend components]

interface ComponentProps {
  // Props definition
}

// Component behavior description

State Management

[How state will be managed]

Error Handling

Security Considerations

• Authentication requirements
• Authorization rules
• Data encryption needs
• Input validation
• Audit logging

Testing Strategy

Unit Tests

• [Component/function to test]
• [Expected coverage]

Integration Tests

• [Integration points to test]

E2E Tests

• [User flows to test]

Performance Tests

• [Load test scenarios]
• [Performance benchmarks]

Migration Plan

Database Migrations

-- Migration: [description]
-- Up
[SQL statements]

-- Down
[Rollback statements]

Data Migration

[Any data transformation needed]

Feature Flags

[Feature flag configuration]

Rollout Plan

Phase 1: [Name]

• Timeline: [Dates]
• Scope: [What's included]
• Success criteria: [Metrics]

Phase 2: [Name]

• Timeline: [Dates]
• Scope: [What's included]
• Success criteria: [Metrics]

Rollback Plan

[How to rollback if issues occur]

Dependencies

External Dependencies

Internal Dependencies

• [Internal dependency 1]
• [Internal dependency 2]

Timeline

Open Questions

• [Question needing resolution]
• [Question needing resolution]

Appendix

Glossary

References

• [Link to related documents]
• [Link to design mockups]

## Complete Example

```markdown
# Technical Specification: User Notification Preferences

**Version:** 1.2
**Author:** Alex Rivera
**Status:** Approved
**Created:** 2025-10-01
**Last Updated:** 2025-10-12

## Overview

### Summary

Implement a notification preferences system allowing users to control which notifications they receive and through which channels (email, push, in-app). Users can set preferences at global and per-category levels.

### Background

Currently, users receive all notifications without ability to customize. User research (Q3 2025) found:
- 67% of users want to reduce notification volume
- 45% have disabled all notifications due to lack of granularity
- Top requested feature in last 3 months

### Goals

- Allow users to enable/disable notifications by category
- Support multiple channels (email, push, in-app)
- Provide sensible defaults for new users
- Enable quiet hours / do not disturb
- Reduce notification-related support tickets by 40%

### Non-Goals

- Notification scheduling (send later) - future feature
- Team/organization-level defaults - separate project
- SMS notifications - not supported in this phase
- Notification templates customization

## Requirements

### Functional Requirements

| ID | Requirement | Priority | Notes |
|----|-------------|----------|-------|
| FR-1 | Users can view all notification categories | Must | Categories from config |
| FR-2 | Users can enable/disable each category | Must | Per channel |
| FR-3 | Users can set global notification on/off | Must | Master switch |
| FR-4 | Users can configure quiet hours | Should | Time zone aware |
| FR-5 | Users can set channel preferences | Must | Email, push, in-app |
| FR-6 | System respects preferences when sending | Must | All notification paths |
| FR-7 | Users can reset to defaults | Could | One-click reset |
| FR-8 | Admins can see preference analytics | Could | Dashboard view |

### Non-Functional Requirements

| ID | Category | Requirement | Target |
|----|----------|-------------|--------|
| NFR-1 | Performance | Preference check latency | < 10ms p99 |
| NFR-2 | Performance | Settings page load time | < 500ms |
| NFR-3 | Availability | Preference service uptime | 99.9% |
| NFR-4 | Scalability | Support concurrent users | 10,000/min |
| NFR-5 | Security | Preferences are user-private | No cross-user access |

### User Stories

#### Story 1: Manage Email Notifications

**As a user, I want to control which emails I receive so that my inbox isn't overwhelmed.**

**Acceptance Criteria:**
- [ ] Given I'm on settings page, when I toggle "Marketing emails" off, then I stop receiving marketing emails
- [ ] Given I disabled an email category, when I re-enable it, then I receive those emails again
- [ ] Given I change preferences, when I save, then I see confirmation message

#### Story 2: Configure Quiet Hours

**As a user, I want to set quiet hours so that I'm not disturbed during off-hours.**

**Acceptance Criteria:**
- [ ] Given I'm on settings, when I enable quiet hours, then I can set start/end times
- [ ] Given quiet hours are active, when a notification would be sent, then push/in-app are suppressed (email still sends)
- [ ] Given my time zone changes, when quiet hours are evaluated, then they use my current time zone

#### Story 3: Disable All Notifications

**As a user, I want a master switch to disable all notifications quickly.**

**Acceptance Criteria:**
- [ ] Given I'm on settings, when I toggle "All notifications" off, then all notification types are disabled
- [ ] Given all notifications are off, when I toggle back on, then my previous per-category settings are restored
- [ ] Given all notifications are off, when system tries to notify, then no notifications are sent

## Technical Design

### Architecture

┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ Web Client │────►│ API Gateway │────►│ Preference Svc │ └─────────────────┘ └─────────────────┘ └────────┬────────┘ │ ┌─────────────────┐ ┌───────▼────────┐ │ Notification │◄─────────────────────────────│ PostgreSQL │ │ Service │ (checks preferences) │ + Redis │ └────────┬────────┘ └────────────────┘ │ ┌────┴────┬──────────┐ ▼ ▼ ▼ ┌─────┐ ┌──────┐ ┌────────┐ │Email│ │ Push │ │ In-App │ └─────┘ └──────┘ └────────┘

### Data Model

```sql
-- User notification preferences
CREATE TABLE notification_preferences (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,

    -- Global settings
    global_enabled BOOLEAN DEFAULT true,
    quiet_hours_enabled BOOLEAN DEFAULT false,
    quiet_hours_start TIME,  -- e.g., '22:00'
    quiet_hours_end TIME,    -- e.g., '08:00'
    timezone VARCHAR(50) DEFAULT 'UTC',

    created_at TIMESTAMP DEFAULT NOW(),
    updated_at TIMESTAMP DEFAULT NOW(),

    UNIQUE(user_id)
);

-- Category-level preferences
CREATE TABLE notification_category_preferences (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    category VARCHAR(50) NOT NULL,  -- e.g., 'comments', 'mentions', 'marketing'

    -- Channel settings
    email_enabled BOOLEAN DEFAULT true,
    push_enabled BOOLEAN DEFAULT true,
    in_app_enabled BOOLEAN DEFAULT true,

    created_at TIMESTAMP DEFAULT NOW(),
    updated_at TIMESTAMP DEFAULT NOW(),

    UNIQUE(user_id, category)
);

-- Indexes
CREATE INDEX idx_notif_pref_user ON notification_preferences(user_id);
CREATE INDEX idx_notif_cat_pref_user ON notification_category_preferences(user_id);

-- Audit log
CREATE TABLE notification_preference_audit (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL,
    changed_field VARCHAR(100),
    old_value TEXT,
    new_value TEXT,
    changed_at TIMESTAMP DEFAULT NOW()
);

API Design

// GET /api/v1/users/me/notification-preferences
interface GetPreferencesResponse {
  global: {
    enabled: boolean;
    quietHours: {
      enabled: boolean;
      start: string | null;  // "22:00"
      end: string | null;    // "08:00"
      timezone: string;
    };
  };
  categories: {
    [category: string]: {
      email: boolean;
      push: boolean;
      inApp: boolean;
    };
  };
  availableCategories: {
    id: string;
    name: string;
    description: string;
    defaultEnabled: boolean;
  }[];
}

// PUT /api/v1/users/me/notification-preferences
interface UpdatePreferencesRequest {
  global?: {
    enabled?: boolean;
    quietHours?: {
      enabled?: boolean;
      start?: string;
      end?: string;
      timezone?: string;
    };
  };
  categories?: {
    [category: string]: {
      email?: boolean;
      push?: boolean;
      inApp?: boolean;
    };
  };
}

interface UpdatePreferencesResponse {
  success: boolean;
  updated: GetPreferencesResponse;
}

// POST /api/v1/users/me/notification-preferences/reset
interface ResetPreferencesResponse {
  success: boolean;
  preferences: GetPreferencesResponse;
}

Component Design

// NotificationPreferences.tsx
interface NotificationPreferencesProps {
  userId: string;
}

interface CategoryToggleProps {
  category: NotificationCategory;
  preferences: CategoryPreference;
  onChange: (category: string, channel: Channel, enabled: boolean) => void;
  disabled: boolean;  // When global is off
}

// State structure
interface PreferencesState {
  loading: boolean;
  saving: boolean;
  error: string | null;
  preferences: Preferences | null;
  pendingChanges: Partial<Preferences>;
}

State Management

Using React Query for server state:

// Queries
const { data: preferences } = useQuery(
  ['notification-preferences'],
  fetchPreferences
);

// Mutations with optimistic updates
const mutation = useMutation(updatePreferences, {
  onMutate: async (newPrefs) => {
    await queryClient.cancelQueries(['notification-preferences']);
    const previous = queryClient.getQueryData(['notification-preferences']);
    queryClient.setQueryData(['notification-preferences'], newPrefs);
    return { previous };
  },
  onError: (err, newPrefs, context) => {
    queryClient.setQueryData(['notification-preferences'], context.previous);
  },
});

Error Handling

Security Considerations

• Authentication: All endpoints require valid JWT
• Authorization: Users can only access their own preferences (user_id from JWT)
• Input validation: Zod schemas for all request bodies
• Rate limiting: 10 preference updates per minute per user
• Audit logging: All preference changes logged with timestamp

Testing Strategy

Unit Tests

Preference Service:

• shouldReturnDefaultsForNewUser
• shouldMergePartialUpdates
• shouldValidateQuietHoursFormat
• shouldHandleTimezoneConversion
• shouldRespectGlobalDisable

Coverage target: 90%

Integration Tests

• API endpoint tests with test database
• Preference check integration with notification service
• Cache invalidation on update

E2E Tests

describe('Notification Preferences', () => {
  it('should disable email notifications', async () => {
    await page.goto('/settings/notifications');
    await page.click('[data-testid="comments-email-toggle"]');
    await page.click('[data-testid="save-button"]');
    await expect(page.locator('.toast-success')).toBeVisible();
  });

  it('should enable quiet hours', async () => {
    await page.goto('/settings/notifications');
    await page.click('[data-testid="quiet-hours-toggle"]');
    await page.fill('[data-testid="quiet-start"]', '22:00');
    await page.fill('[data-testid="quiet-end"]', '08:00');
    await page.click('[data-testid="save-button"]');
    await expect(page.locator('.toast-success')).toBeVisible();
  });
});

Performance Tests

• Load test: 1000 preference reads/second
• Stress test: 100 concurrent preference updates
• Cache hit ratio target: >95%

Migration Plan

Database Migrations

-- Migration: 20251015_create_notification_preferences
-- Up
CREATE TABLE notification_preferences (...);
CREATE TABLE notification_category_preferences (...);
CREATE TABLE notification_preference_audit (...);

-- Create default preferences for existing users
INSERT INTO notification_preferences (user_id, global_enabled)
SELECT id, true FROM users
WHERE id NOT IN (SELECT user_id FROM notification_preferences);

-- Down
DROP TABLE notification_preference_audit;
DROP TABLE notification_category_preferences;
DROP TABLE notification_preferences;

Feature Flags

{
  "notification_preferences_enabled": {
    "type": "boolean",
    "default": false,
    "description": "Enable new notification preferences UI"
  },
  "quiet_hours_enabled": {
    "type": "boolean",
    "default": false,
    "description": "Enable quiet hours feature"
  }
}

Rollout Plan

Phase 1: Internal Testing

• Timeline: Oct 20-24
• Scope: Feature flag on for internal team only
• Success criteria: No critical bugs, <100ms API response

Phase 2: Beta Users

• Timeline: Oct 25-31
• Scope: 5% of users (beta flag)
• Success criteria: <5 bug reports, positive feedback

Phase 3: General Availability

• Timeline: Nov 1-7
• Scope: 100% of users
• Success criteria: Support tickets decrease, no P0/P1 incidents

Rollback Plan

1. Disable feature flag immediately
2. Users see previous settings UI
3. Notification service ignores new preferences table
4. Data preserved for re-rollout

Dependencies

External Dependencies

Internal Dependencies

• User service (for user lookup)
• Notification service (for preference checks)
• Analytics service (for tracking)

Timeline

Open Questions

• Should quiet hours affect email? Resolved: No, emails still send
• Default preferences for existing users? Resolved: All enabled
• Should we add notification frequency limits (daily digest)?

Appendix

Glossary

References

• Design Mockups - Figma
• User Research Report
• Notification Service Documentation
• ADR-045: Notification Architecture

## Best Practices

### 1. Right Level of Detail

**Too vague:** "Build a notification system"
**Too detailed:** Line-by-line code specification
**Just right:** Design decisions, interfaces, data models

### 2. Keep It Updated

- Update status as development progresses
- Add open questions as they arise
- Document decisions made during implementation

### 3. Collaborate Early

- Share draft with key stakeholders
- Get feedback before finalizing
- Include reviewers in the process

### 4. Visual Communication

Use diagrams for:
- Architecture overviews
- Data flows
- State machines
- User flows

### 5. Link to Related Documents

- Design mockups
- RFCs
- ADRs
- API documentation

---

*A good tech spec is a communication tool. It should be detailed enough to implement from, but readable enough for stakeholders to understand.*