PostHog Reference Architecture

Overview

Production-ready architecture patterns for PostHog integrations.

Prerequisites

•Understanding of layered architecture
•PostHog SDK knowledge
•TypeScript project setup
•Testing framework configured

Project Structure

code

my-posthog-project/
├── src/
│   ├── posthog/
│   │   ├── client.ts           # Singleton client wrapper
│   │   ├── config.ts           # Environment configuration
│   │   ├── types.ts            # TypeScript types
│   │   ├── errors.ts           # Custom error classes
│   │   └── handlers/
│   │       ├── webhooks.ts     # Webhook handlers
│   │       └── events.ts       # Event processing
│   ├── services/
│   │   └── posthog/
│   │       ├── index.ts        # Service facade
│   │       ├── sync.ts         # Data synchronization
│   │       └── cache.ts        # Caching layer
│   ├── api/
│   │   └── posthog/
│   │       └── webhook.ts      # Webhook endpoint
│   └── jobs/
│       └── posthog/
│           └── sync.ts         # Background sync job
├── tests/
│   ├── unit/
│   │   └── posthog/
│   └── integration/
│       └── posthog/
├── config/
│   ├── posthog.development.json
│   ├── posthog.staging.json
│   └── posthog.production.json
└── docs/
    └── posthog/
        ├── SETUP.md
        └── RUNBOOK.md

Layer Architecture

code

┌─────────────────────────────────────────┐
│             API Layer                    │
│   (Controllers, Routes, Webhooks)        │
├─────────────────────────────────────────┤
│           Service Layer                  │
│  (Business Logic, Orchestration)         │
├─────────────────────────────────────────┤
│          PostHog Layer        │
│   (Client, Types, Error Handling)        │
├─────────────────────────────────────────┤
│         Infrastructure Layer             │
│    (Cache, Queue, Monitoring)            │
└─────────────────────────────────────────┘

Key Components

Step 1: Client Wrapper

typescript

// src/posthog/client.ts
export class PostHogService {
  private client: PostHogClient;
  private cache: Cache;
  private monitor: Monitor;

  constructor(config: PostHogConfig) {
    this.client = new PostHogClient(config);
    this.cache = new Cache(config.cacheOptions);
    this.monitor = new Monitor('posthog');
  }

  async get(id: string): Promise<Resource> {
    return this.cache.getOrFetch(id, () =>
      this.monitor.track('get', () => this.client.get(id))
    );
  }
}

Step 2: Error Boundary

typescript

// src/posthog/errors.ts
export class PostHogServiceError extends Error {
  constructor(
    message: string,
    public readonly code: string,
    public readonly retryable: boolean,
    public readonly originalError?: Error
  ) {
    super(message);
    this.name = 'PostHogServiceError';
  }
}

export function wrapPostHogError(error: unknown): PostHogServiceError {
  // Transform SDK errors to application errors
}

Step 3: Health Check

typescript

// src/posthog/health.ts
export async function checkPostHogHealth(): Promise<HealthStatus> {
  try {
    const start = Date.now();
    await posthogClient.ping();
    return {
      status: 'healthy',
      latencyMs: Date.now() - start,
    };
  } catch (error) {
    return { status: 'unhealthy', error: error.message };
  }
}

Data Flow Diagram

code

User Request
     │
     ▼
┌─────────────┐
│   API       │
│   Gateway   │
└──────┬──────┘
       │
       ▼
┌─────────────┐    ┌─────────────┐
│   Service   │───▶│   Cache     │
│   Layer     │    │   (Redis)   │
└──────┬──────┘    └─────────────┘
       │
       ▼
┌─────────────┐
│ PostHog    │
│   Client    │
└──────┬──────┘
       │
       ▼
┌─────────────┐
│ PostHog    │
│   API       │
└─────────────┘

Configuration Management

typescript

// config/posthog.ts
export interface PostHogConfig {
  apiKey: string;
  environment: 'development' | 'staging' | 'production';
  timeout: number;
  retries: number;
  cache: {
    enabled: boolean;
    ttlSeconds: number;
  };
}

export function loadPostHogConfig(): PostHogConfig {
  const env = process.env.NODE_ENV || 'development';
  return require(`./posthog.${env}.json`);
}

Instructions

Step 1: Create Directory Structure

Set up the project layout following the reference structure above.

Step 2: Implement Client Wrapper

Create the singleton client with caching and monitoring.

Step 3: Add Error Handling

Implement custom error classes for PostHog operations.

Step 4: Configure Health Checks

Add health check endpoint for PostHog connectivity.

Output

•Structured project layout
•Client wrapper with caching
•Error boundary implemented
•Health checks configured

Error Handling

Issue	Cause	Solution
Circular dependencies	Wrong layering	Separate concerns by layer
Config not loading	Wrong paths	Verify config file locations
Type errors	Missing types	Add PostHog types
Test isolation	Shared state	Use dependency injection

Examples

Quick Setup Script

bash

# Create reference structure
mkdir -p src/posthog/{handlers} src/services/posthog src/api/posthog
touch src/posthog/{client,config,types,errors}.ts
touch src/services/posthog/{index,sync,cache}.ts

Resources

Flagship Skills

For multi-environment setup, see posthog-multi-env-setup.