# Unified API Gateway Design

**Date**: 2025-01-27
**Purpose**: Design document for unified API gateway
**Status**: Design Document

---

## Executive Summary

This document outlines the design for a unified API gateway that will serve as a single entry point for all workspace projects, providing centralized authentication, rate limiting, and API versioning.

---

## Architecture Overview

### Components

1. **API Gateway** (Kong, Traefik, or custom)
2. **Authentication Service** (Keycloak, Auth0, or custom)
3. **Rate Limiting Service** (Redis-based)
4. **API Versioning** (Path-based or header-based)
5. **Monitoring & Logging** (Prometheus, Grafana, Loki)

### Architecture Diagram

```
Client
  ↓
API Gateway (Kong/Traefik)
  ├── Authentication Layer
  ├── Rate Limiting
  ├── Request Routing
  └── Response Aggregation
  ↓
Backend Services
  ├── dbis_core
  ├── the_order
  ├── Sankofa
  └── Other services
```

---

## Features

### 1. Authentication & Authorization

**Methods**:
- JWT tokens
- API keys
- OAuth2/OIDC
- mTLS (for service-to-service)

**Implementation**:
- Centralized authentication service
- Token validation
- Role-based access control (RBAC)
- Permission checking

### 2. Rate Limiting

**Strategies**:
- Per-user rate limits
- Per-API rate limits
- Per-IP rate limits
- Tiered rate limits (free, paid, enterprise)

**Storage**: Redis for distributed rate limiting

### 3. API Versioning

**Strategy**: Path-based versioning
- `/v1/api/...`
- `/v2/api/...`

**Alternative**: Header-based (`Accept: application/vnd.api+json;version=2`)

### 4. Request Routing

**Features**:
- Path-based routing
- Header-based routing
- Load balancing
- Health checks
- Circuit breakers

### 5. Monitoring & Observability

**Metrics**:
- Request rate
- Response times
- Error rates
- Authentication failures
- Rate limit hits

**Logging**:
- All requests logged
- Structured logging (JSON)
- Centralized log aggregation

---

## Technology Options

### Option 1: Kong Gateway (Recommended)

**Pros**:
- Feature-rich
- Plugin ecosystem
- Good documentation
- Enterprise support available

**Cons**:
- More complex setup
- Higher resource usage

### Option 2: Traefik

**Pros**:
- Kubernetes-native
- Auto-discovery
- Simpler setup
- Lower resource usage

**Cons**:
- Fewer built-in features
- Less mature plugin ecosystem

### Option 3: Custom (Node.js/TypeScript)

**Pros**:
- Full control
- Custom features
- Lightweight

**Cons**:
- More development time
- Maintenance burden

**Recommendation**: Kong Gateway for production, Traefik for simpler setups

---

## Implementation Plan

### Phase 1: Basic Gateway (Weeks 1-2)
- [ ] Deploy API gateway (Kong or Traefik)
- [ ] Set up basic routing
- [ ] Configure SSL/TLS
- [ ] Set up monitoring

### Phase 2: Authentication (Weeks 3-4)
- [ ] Integrate authentication service
- [ ] Implement JWT validation
- [ ] Set up RBAC
- [ ] Test authentication flow

### Phase 3: Rate Limiting (Weeks 5-6)
- [ ] Set up Redis for rate limiting
- [ ] Configure rate limit rules
- [ ] Implement tiered limits
- [ ] Test rate limiting

### Phase 4: Advanced Features (Weeks 7-8)
- [ ] API versioning
- [ ] Request/response transformation
- [ ] Caching
- [ ] WebSocket support

### Phase 5: Migration (Weeks 9-12)
- [ ] Migrate dbis_core to gateway
- [ ] Migrate the_order to gateway
- [ ] Migrate Sankofa to gateway
- [ ] Migrate other services
- [ ] Complete testing

---

## Configuration Example

### Kong Gateway Configuration

```yaml
services:
  - name: dbis-core
    url: http://dbis-core:3000
    routes:
      - name: dbis-core-v1
        paths:
          - /v1/dbis
        plugins:
          - name: rate-limiting
            config:
              minute: 100
              hour: 1000
          - name: jwt
            config:
              secret_is_base64: false
```

### Traefik Configuration

```yaml
http:
  routers:
    dbis-core:
      rule: "PathPrefix(`/v1/dbis`)"
      service: dbis-core
      middlewares:
        - auth
        - rate-limit
  services:
    dbis-core:
      loadBalancer:
        servers:
          - url: "http://dbis-core:3000"
```

---

## Security Considerations

### Authentication
- JWT tokens with short expiration
- Refresh token rotation
- Token revocation
- Secure token storage

### Rate Limiting
- Prevent DDoS attacks
- Protect against abuse
- Fair resource allocation

### Network Security
- mTLS for service-to-service
- WAF (Web Application Firewall)
- DDoS protection
- IP whitelisting (optional)

---

## Monitoring & Alerting

### Key Metrics
- Request rate per service
- Response times (p50, p95, p99)
- Error rates
- Authentication failures
- Rate limit hits
- Gateway health

### Alerts
- High error rate
- Slow response times
- Authentication failures spike
- Rate limit exhaustion
- Gateway downtime

---

## Success Metrics

- [ ] Single entry point for all APIs
- [ ] Centralized authentication operational
- [ ] Rate limiting functional
- [ ] 80% of projects migrated to gateway
- [ ] 50% reduction in authentication code duplication
- [ ] Improved API security posture

---

**Last Updated**: 2025-01-27
**Next Review**: After Phase 1 completion