PRD: API & Technical Architecture

Generated: 2025-07-23 00:00 UTC
Status: Complete
Verified:

Executive Summary

This PRD defines the API design and technical architecture for the Document Conversion Service. It establishes standards for RESTful API endpoints, asynchronous processing patterns, webhook systems, SDKs, and the underlying microservices architecture that enables scalable, reliable document conversions.

Key Objectives

Design intuitive, developer-friendly REST APIs
Implement robust asynchronous processing for large files
Provide comprehensive webhook notifications
Build modular, scalable microservices architecture
Ensure high availability and fault tolerance

User Stories

As an API Developer

I want clear, consistent API endpoints for all conversion types
I want comprehensive API documentation with examples
I want proper error messages and status codes
I want to track conversion progress via webhooks

As a System Integrator

I want SDKs in multiple programming languages
I want batch processing capabilities
I want to handle rate limiting gracefully
I want detailed API logs for debugging

As a DevOps Engineer

I want containerized, stateless services
I want horizontal scaling capabilities
I want comprehensive monitoring endpoints
I want zero-downtime deployments

Functional Requirements

RESTful API Design

1. Core Endpoints

POST /convert

Primary conversion endpoint supporting all formats

POST /api/v1/convert
Content-Type: multipart/form-data

Parameters:
- file: binary (required)
- from: string (auto-detect if not specified)
- to: string (required) - json|markdown|html
- options: object (optional) - format-specific options

POST /convert/async

Asynchronous conversion for large files

POST /api/v1/convert/async
Content-Type: multipart/form-data

Parameters:
- file: binary (required)
- from: string (optional)
- to: string (required)
- webhook_url: string (required)
- options: object (optional)

Response:
{
  "job_id": "uuid",
  "status": "queued",
  "estimated_time": 30
}

GET /convert/status/{job_id}

Check async conversion status

GET /api/v1/convert/status/{job_id}

Response:
{
  "job_id": "uuid",
  "status": "processing|completed|failed",
  "progress": 75,
  "result_url": "https://...",
  "error": null
}

POST /convert/batch

Batch conversion endpoint

POST /api/v1/convert/batch
Content-Type: application/json

Body:
{
  "conversions": [
    {
      "source_url": "https://...",
      "from": "xlsx",
      "to": "json",
      "options": {}
    }
  ],
  "webhook_url": "https://..."
}

2. Format-Specific Endpoints

Excel Conversions

POST /api/v1/convert/xlsx
POST /api/v1/convert/xlsx/sheets - List sheets
POST /api/v1/convert/xlsx/preview - Preview data

PDF Conversions

POST /api/v1/convert/pdf
POST /api/v1/convert/pdf/pages - Extract specific pages
POST /api/v1/convert/pdf/ocr - With OCR processing

Word Conversions

POST /api/v1/convert/docx
POST /api/v1/convert/docx/styles - Preserve specific styles

PowerPoint Conversions

POST /api/v1/convert/pptx
POST /api/v1/convert/pptx/slides - Convert specific slides

API Standards

1. Request/Response Format

JSON API specification compliance
Consistent error response structure
Pagination for list endpoints
Field filtering support

2. Status Codes

200: Successful conversion
202: Async job accepted
400: Invalid input/parameters
413: File too large
422: Unsupported format
429: Rate limit exceeded
500: Server error

3. Error Response Format

{
  "error": {
    "code": "INVALID_FORMAT",
    "message": "The uploaded file is not a valid XLSX file",
    "details": {
      "supported_formats": ["xlsx", "xls"],
      "detected_format": "pdf"
    }
  }
}

Webhook System

1. Webhook Events

conversion.started
conversion.progress
conversion.completed
conversion.failed
batch.completed

2. Webhook Payload

{
  "event": "conversion.completed",
  "timestamp": "2025-07-23T10:00:00Z",
  "data": {
    "job_id": "uuid",
    "result_url": "https://...",
    "expires_at": "2025-07-23T11:00:00Z",
    "metadata": {
      "pages": 10,
      "processing_time": 5.2
    }
  }
}

3. Webhook Security

HMAC signature verification
Retry logic with exponential backoff
Webhook endpoint validation
Event deduplication

SDK Requirements

1. Language Support

JavaScript/TypeScript (Node.js & Browser)
Python
Java
Go
PHP
Ruby

2. SDK Features

Automatic retry logic
Progress tracking
Streaming support
Type definitions
Comprehensive examples

3. SDK Example (JavaScript)

const converter = new DocumentConverter({
  apiKey: 'your-api-key',
  region: 'eu-west-1'
});

// Synchronous conversion
const result = await converter.convert({
  file: fileBuffer,
  from: 'xlsx',
  to: 'json',
  options: {
    sheets: ['Sheet1', 'Sheet2']
  }
});

// Asynchronous with progress
const job = await converter.convertAsync({
  file: largeFile,
  to: 'markdown',
  onProgress: (progress) => console.log(`${progress}% complete`)
});

Non-Functional Requirements

Architecture Principles

1. Microservices Design

Service per conversion type
Shared libraries for common functionality
Independent deployment and scaling
Service mesh for communication

2. Stateless Services

No session state in services
External storage for temporary files
Distributed caching layer
Configuration via environment

3. Event-Driven Architecture

Message queues for async processing
Event streaming for real-time updates
CQRS for read/write separation
Event sourcing for audit trail

Scalability Architecture

graph TB A[API Gateway] --> B[Load Balancer] B --> C[API Servers] C --> D[Message Queue] D --> E[Worker Pool] E --> F[Object Storage] C --> G[Cache Layer] C --> H[Database] E --> I[Webhook Service] I --> J[External Systems]

High Availability

1. Redundancy

Multi-AZ deployment
Active-active configuration
Database replication
Cross-region backup

2. Fault Tolerance

Circuit breakers
Graceful degradation
Automatic failover
Health check endpoints

3. Disaster Recovery

RPO: < 1 hour
RTO: < 2 hours
Automated backup
Tested recovery procedures

Technical Specifications

API Gateway Configuration

1. Rate Limiting

100 requests/minute (free tier)
1,000 requests/minute (pro tier)
10,000 requests/minute (enterprise)
Burst allowance: 2x limit

2. Authentication

API key authentication
JWT for user sessions
OAuth 2.0 support
IP whitelisting (enterprise)

3. Request Routing

Path-based routing
Header-based routing
Geographic routing
A/B testing support

Service Architecture

1. Container Specifications

services:
  api-server:
    image: converter-api:latest
    replicas: 3-10
    resources:
      cpu: 2
      memory: 4Gi
    
  xlsx-worker:
    image: xlsx-converter:latest
    replicas: 5-20
    resources:
      cpu: 4
      memory: 8Gi

2. Queue Configuration

SQS/Cloud Tasks for job queuing
Redis for real-time updates
Kafka for event streaming
RabbitMQ for complex routing

3. Storage Architecture

S3/GCS for file storage
Redis for caching
PostgreSQL for metadata
ElasticSearch for search

Monitoring & Observability

1. Metrics Collection

API response times
Conversion success rates
Queue depths
Resource utilization

2. Logging Strategy

Structured JSON logs
Correlation IDs
Log aggregation
Real-time analysis

3. Tracing

Distributed tracing
Request flow visualization
Performance bottleneck identification
Error tracking

Success Metrics

API Performance

P50 latency < 100ms
P99 latency < 1s
API availability > 99.9%
Error rate < 0.1%

Conversion Performance

Sync conversion < 10s
Async job acceptance < 1s
Webhook delivery > 99%
SDK adoption > 50%

Developer Experience

API documentation rating > 4.5/5
SDK satisfaction > 4/5
Support response time < 2 hours
Integration time < 1 day

Dependencies

External Services

Cloud provider APIs
CDN services
Monitoring platforms
Authentication providers

Internal Services

User management service
Billing service
Analytics service
Support system

Timeline & Milestones

Phase 1: Core API (Months 1-2)

Basic REST endpoints
Synchronous conversions
API documentation
Rate limiting

Phase 2: Async & Webhooks (Months 2-3)

Asynchronous processing
Webhook system
Job status tracking
Batch processing

Phase 3: SDKs (Months 3-4)

JavaScript/TypeScript SDK
Python SDK
SDK documentation
Code examples

Phase 4: Advanced Features (Months 4-6)

GraphQL API
WebSocket support
Streaming conversions
Advanced routing

Risk Mitigation

Technical Risks

API abuse: Implement rate limiting and DDoS protection
Service cascading failures: Circuit breakers and bulkheads
Data consistency: Implement idempotency and transactions

Operational Risks

Deployment failures: Blue-green deployments
Configuration drift: Infrastructure as code
Security vulnerabilities: Regular security audits

Future Considerations

API Evolution

GraphQL endpoint
gRPC for internal services
WebSocket for real-time updates
HTTP/3 support

Advanced Features

API composition layer
Smart routing based on file type
Predictive scaling
Edge computing deployment