PostHog Core Workflow B — Feature Flags & Experiments

Overview

Feature flag management, A/B experiment evaluation, and cohort analysis with PostHog. Covers boolean and multivariate flags, local evaluation for performance, experiment setup and statistical significance, and cohort creation via the API.

Prerequisites

• Completed posthog-install-auth setup
• Familiarity with posthog-core-workflow-a (event capture)
• Personal API key (phx_...) for flag management API

Instructions

Step 1: Evaluate Feature Flags (Browser)

import posthog from 'posthog-js';

// Boolean flag
if (posthog.isFeatureEnabled('new-checkout-flow')) {
  renderNewCheckout();
} else {
  renderLegacyCheckout();
}

// Multivariate flag (returns string variant name)
const variant = posthog.getFeatureFlag('pricing-page-experiment');
switch (variant) {
  case 'control':
    renderOriginalPricing();
    break;
  case 'annual-first':
    renderAnnualFirstPricing();
    break;
  case 'social-proof':
    renderSocialProofPricing();
    break;
  default:
    renderOriginalPricing(); // Fallback if flag not loaded yet
}

// Get flag payload (JSON data attached to a flag variant)
const payload = posthog.getFeatureFlagPayload('banner-config');
// payload: { text: "Spring sale!", color: "#ff6b35", discount: 20 }

// React: Wait for flags to load before rendering
posthog.onFeatureFlags(() => {
  // Flags are now loaded and ready
  const enabled = posthog.isFeatureEnabled('new-feature');
  setFeatureEnabled(enabled ?? false);
});

Step 2: Evaluate Feature Flags (Server — posthog-node)

import { PostHog } from 'posthog-node';

const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
  // Personal API key enables local evaluation (no network call per flag check)
  personalApiKey: process.env.POSTHOG_PERSONAL_API_KEY,
});

// Single flag evaluation
async function checkFlag(userId: string): Promise<boolean> {
  const enabled = await posthog.isFeatureEnabled('new-api-version', userId);
  return enabled ?? false;
}

// Multivariate flag
async function getVariant(userId: string): Promise<string> {
  const variant = await posthog.getFeatureFlag('onboarding-experiment', userId, {
    personProperties: { plan: 'pro', country: 'US' },
  });
  return (variant as string) || 'control';
}

// Get ALL flags for a user at once (one network call)
async function getUserFlags(userId: string) {
  const flags = await posthog.getAllFlags(userId, {
    personProperties: { plan: 'enterprise' },
    groupProperties: { company: { name: 'Acme' } },
  });
  // flags: { 'new-checkout': true, '

PostHog Cost Tuning

Overview

PostHog Cloud pricing is event-based: 1M events/month free, then usage-based pricing beyond that. Session recordings, feature flag evaluations, and surveys each have their own free tiers. The biggest cost drivers are typically $autocapture events, $pageview on high-traffic pages, and bot traffic. This skill covers specific techniques to reduce event volume without losing analytical value.

Prerequisites

• PostHog Cloud account with billing access
• Application instrumented with posthog-js
• Understanding of which events drive your analytics

PostHog Cloud Free Tiers (2025)

Instructions

Step 1: Audit Current Event Volume

set -euo pipefail
# See which events consume the most quota (last 30 days)
curl "https://app.posthog.com/api/projects/$POSTHOG_PROJECT_ID/query/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "query": {
      "kind": "HogQLQuery",
      "query": "SELECT event, count() AS total FROM events WHERE timestamp > now() - interval 30 day GROUP BY event ORDER BY total DESC LIMIT 20"
    }
  }' | jq '.results[] | {event: .[0], count: .[1]}'

Step 2: Tune Autocapture

$autocapture is often the largest event volume. Restrict it to only useful interactions.

import posthog from 'posthog-js';

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  api_host: 'https://us.i.posthog.com',
  autocapture: {
    // Only capture click and submit events (skip change, scroll, etc.)
    dom_event_allowlist: ['click', 'submit'],
    // Only capture meaningful elements
    element_allowlist: ['a', 'button', 'form', 'input[type=submit]'],
    // Only capture elements with this CSS class
    css_selector_allowlist: ['.track-click', '[data-track]'],
    // Skip internal/admin pages entirely
    url_ignorelist: ['/admin', '/health', '/api/internal', '/_next'],
  },
});

Step 3: Event Sampling with before_send

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  api_host: 'https://us.i.posthog.com',
  before_send: (event) => 

PostHog Data Handling

Overview

Privacy-safe analytics with PostHog. Covers property sanitization to strip PII before events leave the browser, consent-based tracking (opt-in/opt-out), GDPR data subject access requests and deletion, and PostHog's built-in privacy controls (IP masking, session recording masking).

Prerequisites

• PostHog project (Cloud or self-hosted)
• posthog-js and/or posthog-node installed
• Privacy policy covering analytics data collection
• Cookie consent mechanism (e.g., CookieConsent banner)

Instructions

Step 1: Privacy-Safe Initialization

import posthog from 'posthog-js';

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  api_host: 'https://us.i.posthog.com',

  // Disable autocapture to control exactly what's captured
  autocapture: false,

  // Respect browser Do Not Track setting
  respect_dnt: true,

  // Don't capture until user consents
  opt_out_capturing_by_default: false, // Set true for opt-in model

  // Sanitize ALL properties before they leave the browser
  sanitize_properties: (properties, eventName) => {
    // Remove IP address
    delete properties['$ip'];

    // Remove potentially identifying properties
    delete properties['$device_id'];

    // Redact URLs containing tokens or auth info
    if (properties['$current_url']) {
      properties['$current_url'] = properties['$current_url']
        .replace(/token=[^&]+/g, 'token=[REDACTED]')
        .replace(/key=[^&]+/g, 'key=[REDACTED]')
        .replace(/session=[^&]+/g, 'session=[REDACTED]');
    }

    // Redact referrer tokens
    if (properties['$referrer']) {
      properties['$referrer'] = properties['$referrer']
        .replace(/token=[^&]+/g, 'token=[REDACTED]');
    }

    return properties;
  },

  // Session recording privacy
  session_recording: {
    maskAllInputs: true,           // Mask all input fields
    maskTextSelector: '.pii-data', // Mask specific elements
  },
});

Step 2: Consent-Based Tracking

// Cookie consent integration
interface ConsentState {
  analytics: boolean;
  functional: boolean;
  marketing: boolean;
}

export function handleConsentChange(consent: ConsentState) {
  if (consent.analytics) {
    // User opted in — start capturing
    posthog.opt_in_capturing();
  } else {
    // User opted out — stop capturing and clear local data
    posthog.opt_out_capturing();
    posthog.reset(); // Clears distinct_id, device_id, session data
  }
}

// Check consent before identifying (PII)
export function identifyWithConsent(
  userId: string,
  properties: Record<string, any>,
  hasAnalyticsConsent: boolean
) {
  if (!hasAnalyticsConsent) return;

  // Only send non-PI

PostHog Debug Bundle

Current State

!node --version 2>/dev/null || echo 'N/A'

!npm list posthog-js posthog-node 2>/dev/null | grep posthog || echo 'No PostHog SDK found'

Overview

Collect diagnostic evidence for PostHog support tickets. Gathers SDK versions, API connectivity, feature flag status, event flow verification, and redacted configuration. All secrets are automatically redacted.

Prerequisites

• PostHog SDK installed in project
• Access to environment variables
• curl and jq available

Instructions

Step 1: Run Full Diagnostic Script

#!/bin/bash
set -euo pipefail

BUNDLE_DIR="posthog-debug-$(date +%Y%m%d-%H%M%S)"
mkdir -p "$BUNDLE_DIR"

echo "=== PostHog Debug Bundle ===" > "$BUNDLE_DIR/summary.txt"
echo "Generated: $(date -u +%Y-%m-%dT%H:%M:%SZ)" >> "$BUNDLE_DIR/summary.txt"
echo "" >> "$BUNDLE_DIR/summary.txt"

# --- Environment ---
echo "--- Runtime Environment ---" >> "$BUNDLE_DIR/summary.txt"
echo "Node: $(node --version 2>/dev/null || echo 'not found')" >> "$BUNDLE_DIR/summary.txt"
echo "npm: $(npm --version 2>/dev/null || echo 'not found')" >> "$BUNDLE_DIR/summary.txt"
echo "Python: $(python3 --version 2>/dev/null || echo 'not found')" >> "$BUNDLE_DIR/summary.txt"
echo "OS: $(uname -srm)" >> "$BUNDLE_DIR/summary.txt"
echo "" >> "$BUNDLE_DIR/summary.txt"

# --- SDK Versions ---
echo "--- PostHog SDK Versions ---" >> "$BUNDLE_DIR/summary.txt"
npm list posthog-js posthog-node 2>/dev/null >> "$BUNDLE_DIR/summary.txt" || echo "No npm PostHog packages" >> "$BUNDLE_DIR/summary.txt"
pip3 show posthog 2>/dev/null | grep -E "Name|Version" >> "$BUNDLE_DIR/summary.txt" || true
echo "" >> "$BUNDLE_DIR/summary.txt"

# --- API Connectivity ---
echo "--- API Connectivity ---" >> "$BUNDLE_DIR/summary.txt"
echo -n "US Cloud ingest: " >> "$BUNDLE_DIR/summary.txt"
curl -s -o /dev/null -w "%{http_code} (%{time_total}s)" https://us.i.posthog.com/healthz >> "$BUNDLE_DIR/summary.txt" 2>&1
echo "" >> "$BUNDLE_DIR/summary.txt"
echo -n "EU Cloud ingest: " >> "$BUNDLE_DIR/summary.txt"
curl -s -o /dev/null -w "%{http_code} (%{time_total}s)" https://eu.i.posthog.com/healthz >> "$BUNDLE_DIR/summary.txt" 2>&1
echo "" >> "$BUNDLE_DIR/summary.txt"
echo -n "App API: " >> &quo

PostHog Deploy Integration

Overview

Deploy PostHog analytics to production platforms. Covers Next.js with Vercel (reverse proxy, server-side capture, edge functions), self-hosted PostHog with Docker, and Google Cloud Run deployment patterns.

Prerequisites

• PostHog project API key (phc_...)
• PostHog personal API key (phx_...) for server features
• Platform CLI installed (vercel, docker, or gcloud)

Instructions

Step 1: Next.js + Vercel Deployment

set -euo pipefail
# Set environment variables in Vercel
vercel env add NEXT_PUBLIC_POSTHOG_KEY production     # phc_... (public)
vercel env add NEXT_PUBLIC_POSTHOG_HOST production    # /ingest (if using proxy)
vercel env add POSTHOG_PERSONAL_API_KEY production    # phx_... (server-only)
vercel env add POSTHOG_PROJECT_ID production          # Project ID number

// next.config.js — Reverse proxy to bypass ad blockers
module.exports = {
  async rewrites() {
    return [
      {
        source: '/ingest/static/:path*',
        destination: 'https://us-assets.i.posthog.com/static/:path*',
      },
      {
        source: '/ingest/:path*',
        destination: 'https://us.i.posthog.com/:path*',
      },
    ];
  },
};

// app/providers.tsx — Client-side PostHog with proxy
'use client';
import posthog from 'posthog-js';
import { PostHogProvider } from 'posthog-js/react';
import { useEffect } from 'react';

export function PHProvider({ children }: { children: React.ReactNode }) {
  useEffect(() => {
    posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
      api_host: '/ingest', // Routes through your domain's reverse proxy
      capture_pageview: false, // Handle manually in App Router
      capture_pageleave: true,
    });
  }, []);

  return <PostHogProvider client={posthog}>{children}</PostHogProvider>;
}

Step 2: Server-Side Capture in Vercel Edge Functions

// app/api/track/route.ts — Server-side event capture
import { PostHog } from 'posthog-node';
import { NextResponse } from 'next/server';

export const runtime = 'edge';

export async function POST(request: Request) {
  const body = await request.json();
  const { userId, event, properties } = body;

  const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
    host: 'https://us.i.posthog.com',
    flushAt: 1,       // Immediate flush in serverless
    flushInterval: 0,
  });

  try {
    posthog.capture({ distinctId: userId, event, properties });
    await posthog.shutdown(); // CRITICAL: flush before function exits
    return NextResponse.json({ status: 'ok' });
  } catch (error) {
  

PostHog Enterprise RBAC

Overview

PostHog access control uses a three-level hierarchy: Organization > Project > Resource. Organizations contain multiple projects (e.g., production, staging), and each project has its own data, feature flags, and dashboards. Members are assigned roles at the organization level and can be restricted to specific projects.

Prerequisites

• PostHog Cloud or self-hosted with enterprise license
• Organization admin role
• Multiple projects configured (one per environment)

Access Control Model

Member Roles:

Instructions

Step 1: Set Up Project-Level Access

set -euo pipefail
# Create a production project with access control
curl -X POST "https://app.posthog.com/api/organizations/$ORG_ID/projects/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name": "Production", "access_control": true}'

# Add a member to a specific project (level 1 = Member, 8 = Admin)
curl -X POST "https://app.posthog.com/api/projects/$PROD_PROJECT_ID/members/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"user_id": "USER_UUID", "level": 1}'

# List current project members
curl "https://app.posthog.com/api/projects/$PROD_PROJECT_ID/members/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" | \
  jq '.results[] | {email: .user.email, level, joined_at}'

Step 2: Create Scoped API Keys

set -euo pipefail
# Read-only key for BI dashboard integration
curl -X POST "https://app.posthog.com/api/personal_api_keys/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "label": "bi-dashboard-readonly",
    "scopes": ["insight:read", "dashboard:read", "query:read"]

PostHog Hello World

Overview

Minimal working examples demonstrating the three core PostHog operations: capturing events, identifying users, and evaluating feature flags. Covers both browser (posthog-js) and server (posthog-node) SDKs.

Prerequisites

• Completed posthog-install-auth setup
• Project API key (phc_...) configured
• posthog-js and/or posthog-node installed

Instructions

Step 1: Capture Your First Event (Node.js)

// hello-posthog.ts
import { PostHog } from 'posthog-node';

const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
});

async function main() {
  // 1. Capture a custom event
  posthog.capture({
    distinctId: 'user-123',
    event: 'hello_posthog',
    properties: {
      greeting: 'Hello from posthog-node!',
      source: 'hello-world-skill',
      timestamp: new Date().toISOString(),
    },
  });
  console.log('Event captured: hello_posthog');

  // 2. Identify a user with properties
  posthog.identify({
    distinctId: 'user-123',
    properties: {
      email: 'dev@example.com',
      name: 'Dev User',
      plan: 'free',
    },
  });
  console.log('User identified: user-123');

  // 3. Check a feature flag
  const flagValue = await posthog.getFeatureFlag('my-feature-flag', 'user-123');
  console.log(`Feature flag "my-feature-flag": ${flagValue}`);

  // 4. Flush and shutdown (required in scripts/serverless)
  await posthog.shutdown();
  console.log('Done — check app.posthog.com Activity tab');
}

main().catch(console.error);

Step 2: Browser Hello World (posthog-js)

// In a React component or vanilla JS
import posthog from 'posthog-js';

// Initialize (call once at app startup)
posthog.init('phc_your_project_key', {
  api_host: 'https://us.i.posthog.com',
  loaded: () => console.log('PostHog loaded'),
});

// Capture a custom event
posthog.capture('button_clicked', {
  button_name: 'signup',
  page: window.location.pathname,
});

// Identify the user after login
posthog.identify('user-123', {
  email: 'user@example.com',
  plan: 'pro',
});

// Check a feature flag
if (posthog.isFeatureEnabled('new-checkout')) {
  console.log('New checkout flow is enabled');
}

// Associate user with a company (group analytics)
posthog.group('company', 'company-456', {
  name: 'Acme Corp',
  plan: 'enterprise',
});

Step 3: Python Hello World

import posthog

posthog.project_api_key = 'phc_your_project_key'
posthog.host = 'https:/

PostHog Incident Runbook

Overview

Rapid incident response for PostHog integration failures. PostHog Cloud has its own status page (status.posthog.com) — the first step is always determining whether the issue is PostHog-side or your integration.

Severity Levels

Quick Triage (Run First)

set -euo pipefail
echo "=== PostHog Triage ==="
echo ""

# 1. Is PostHog Cloud up?
echo -n "PostHog US Cloud: "
curl -sf -o /dev/null -w "%{http_code}" https://us.i.posthog.com/healthz || echo "UNREACHABLE"
echo ""

# 2. Can we capture events?
echo -n "Event capture: "
curl -sf -o /dev/null -w "%{http_code}" -X POST 'https://us.i.posthog.com/capture/' \
  -H 'Content-Type: application/json' \
  -d "{\"api_key\":\"${NEXT_PUBLIC_POSTHOG_KEY}\",\"event\":\"triage_test\",\"distinct_id\":\"triage\"}" || echo "FAILED"
echo ""

# 3. Can we evaluate flags?
echo -n "Flag evaluation: "
curl -sf -o /dev/null -w "%{http_code}" -X POST 'https://us.i.posthog.com/decide/?v=3' \
  -H 'Content-Type: application/json' \
  -d "{\"api_key\":\"${NEXT_PUBLIC_POSTHOG_KEY}\",\"distinct_id\":\"triage\"}" || echo "FAILED"
echo ""

# 4. Can we access admin API?
if [ -n "${POSTHOG_PERSONAL_API_KEY:-}" ]; then
  echo -n "Admin API: "
  curl -sf -o /dev/null -w "%{http_code}" "https://app.posthog.com/api/projects/" \
    -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" || echo "FAILED"
  echo ""
fi

# 5. Check our integration health
echo -n "Our health endpoint: "
curl -sf -o /dev/null -w "%{http_code}" "https://your-app.com/api/health" || echo "UNREACHABLE"
echo ""

Decision Tree

Is PostHog Cloud healthy (status.posthog.com)?
├── NO → PostHog outage
│   ├── Enable graceful degradation (feature flags return defaults)
│   ├── Monitor status.posthog.com for resolution
│   └── Events will be lost during outage (capture is fire-and-forget)
│
└── YES → Our integratio

PostHog Install & Auth

Overview

Install PostHog SDKs and configure authentication. PostHog uses two key types: Project API Key (phc...) for event capture (public, safe for frontend) and Personal API Key (phx...) for private API endpoints (never expose to clients).

Prerequisites

• Node.js 20+ or Python 3.10+
• PostHog account at app.posthog.com
• Project API key from Project Settings > Project API Key
• Personal API key from Settings > Personal API Keys (for server-side admin)

Instructions

Step 1: Install the SDK

set -euo pipefail
# Browser SDK (posthog-js)
npm install posthog-js

# Node.js server SDK (posthog-node)
npm install posthog-node

# Python SDK
pip install posthog

Step 2: Configure Environment Variables

# .env (add to .gitignore — never commit)
NEXT_PUBLIC_POSTHOG_KEY=phc_your_project_api_key    # Safe for frontend
POSTHOG_HOST=https://us.i.posthog.com               # US Cloud (or eu.i.posthog.com)
POSTHOG_PERSONAL_API_KEY=phx_your_personal_key      # Server-only, never expose
POSTHOG_PROJECT_ID=12345                             # From project URL

Step 3: Initialize Browser SDK (posthog-js)

// lib/posthog.ts
import posthog from 'posthog-js';

export function initPostHog() {
  if (typeof window === 'undefined') return;

  posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
    api_host: process.env.NEXT_PUBLIC_POSTHOG_HOST || 'https://us.i.posthog.com',
    capture_pageview: true,        // Auto-capture $pageview
    capture_pageleave: true,       // Auto-capture $pageleave
    autocapture: true,             // Auto-capture clicks, inputs, form submits
    persistence: 'localStorage+cookie',
    loaded: (ph) => {
      if (process.env.NODE_ENV === 'development') {
        ph.debug();  // Logs all events to console
      }
    },
  });
}

Step 4: Initialize Server SDK (posthog-node)

// lib/posthog-server.ts
import { PostHog } from 'posthog-node';

let client: PostHog | null = null;

export function getPostHog(): PostHog {
  if (!client) {
    client = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
      host: process.env.POSTHOG_HOST || 'https://us.i.posthog.com',
      flushAt: 20,           // Send batch when 20 events queued
      flushInterval: 10000,  // Or every 10 seconds
      personalApiKey: process.env.POSTHOG_PERSONAL_API_KEY, // Enables local flag eval
    });
  }
  return client;
}

// CRITICAL: Flush before process exits (especially in serverless)
export async function shutdownPostHog() {
  if (client) {
    await client.shutdown();
    client = null;
  }
}

PostHog Migration Deep Dive

Current State

!npm list posthog-js posthog-node 2>/dev/null | grep posthog || echo 'No PostHog SDK found'

!npm list @segment/analytics-node mixpanel @google-analytics/data 2>/dev/null | grep -E "segment|mixpanel|google" || echo 'No competitor SDKs found'

Overview

Migrate from Google Analytics, Mixpanel, Amplitude, or Segment to PostHog using a dual-write strategy (send events to both old and new platforms) followed by gradual traffic shifting. PostHog's capture API accepts events in a format similar to Segment's track/identify calls, making migration straightforward.

Migration Types

Instructions

Step 1: Event Name Mapping

// migration/event-map.ts
// Map old event names to PostHog event taxonomy
const EVENT_MAP: Record<string, string> = {
  // Mixpanel → PostHog
  'Sign Up': 'user_signed_up',
  'Login': 'user_logged_in',
  'Page View': '$pageview',
  'Button Click': 'button_clicked',
  'Purchase': 'payment_completed',
  'Subscription Started': 'subscription_started',

  // GA4 → PostHog
  'page_view': '$pageview',
  'sign_up': 'user_signed_up',
  'login': 'user_logged_in',
  'purchase': 'payment_completed',
  'add_to_cart': 'item_added_to_cart',

  // Amplitude → PostHog
  'Page Viewed': '$pageview',
  'Signed Up': 'user_signed_up',
  'Feature Used': 'feature_used',
};

// Property name mapping
const PROPERTY_MAP: Record<string, string> = {
  // Mixpanel → PostHog
  '$email': 'email',
  '$name': 'name',
  '$city': 'city',
  'Plan': 'plan',
  'MRR': 'mrr',

  // GA4 → PostHog
  'page_title': '$title',
  'page_location': '$current_url',
  'page_referrer': '$referrer',
};

Step 2: Dual-Write Adapter

// migration/analytics-adapter.ts
import { PostHog } from 'posthog-node';
import Mixpanel from 'mixpanel'; // or y

PostHog Multi-Environment Setup

Overview

Use separate PostHog projects for each environment (dev, staging, production). This prevents dev/test events from polluting production analytics, allows different feature flag rollout percentages per environment, and lets you disable session recordings in non-production.

Prerequisites

• PostHog Cloud account or self-hosted instance
• Admin access to create multiple projects
• Deployment platform with environment variable support

Environment Strategy

Instructions

Step 1: Create Separate PostHog Projects

In PostHog Cloud (app.posthog.com), create three projects:

1. myapp-development — copy the phc_... project API key
2. myapp-staging — copy the phc_... project API key
3. myapp-production — copy the phc_... project API key

Step 2: Environment Variables

# .env.local (development — git-ignored)
NEXT_PUBLIC_POSTHOG_KEY=phc_dev_key_here
NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com
POSTHOG_PERSONAL_API_KEY=phx_your_key
POSTHOG_PROJECT_ID=11111

# .env.staging (CI/CD secrets or secret manager)
NEXT_PUBLIC_POSTHOG_KEY=phc_staging_key_here
NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com
POSTHOG_PERSONAL_API_KEY=phx_your_key
POSTHOG_PROJECT_ID=22222

# Production (secret manager — never in files)
# NEXT_PUBLIC_POSTHOG_KEY=phc_prod_key_here
# POSTHOG_PROJECT_ID=33333

Step 3: Environment-Aware SDK Configuration

// config/posthog.ts
type Env = 'development' | 'staging' | 'production';

interface PostHogEnvConfig {
  apiKey: string;
  host: string;
  sessionRecording: boolean;
  recordingSampleRate: number;
  autocapture: boolean | object;
  debug: boolean;
}

function getConfig(): PostHogEnvConfig {
  const env = (process.env.NODE_ENV || 'development') as Env;
  const key = process.env.NEXT_PUBLIC_POSTHOG_KEY;
  const host = process.env.NEXT_PUBLIC_POSTHOG_HOST || 'https://us.i.posthog.com';

  if (!key) {
    console.warn(`[PostHog] No API key for ${env} — analytics disabled`);
  }

  const configs: Record<Env, Omit<PostHogEnvConfig, 'apiKey' | 'host'>> = {
    development: {
      sessionRecording:

PostHog Observability

Overview

Monitor PostHog integration health with four key signals: event ingestion rate (are events flowing?), feature flag evaluation latency (are flags fast enough for hot paths?), event volume by type (detect instrumentation regressions), and API rate limit consumption (are we approaching 429s?).

Prerequisites

• PostHog project with personal API key (phx_...)
• Application instrumented with PostHog SDK
• Prometheus/Grafana or equivalent monitoring stack (optional)

Instructions

Step 1: Event Ingestion Health Check

set -euo pipefail
# Check if events are flowing (last 24 hours)
curl "https://app.posthog.com/api/projects/$POSTHOG_PROJECT_ID/query/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "query": {
      "kind": "HogQLQuery",
      "query": "SELECT toStartOfHour(timestamp) AS hour, count() AS events FROM events WHERE timestamp > now() - interval 24 hour GROUP BY hour ORDER BY hour"
    }
  }' | jq '.results | map({hour: .[0], events: .[1]}) | .[-3:]'

Step 2: Instrument Flag Evaluation Latency

// posthog-instrumented.ts
import { PostHog } from 'posthog-node';

const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
  personalApiKey: process.env.POSTHOG_PERSONAL_API_KEY,
});

// Wrap flag evaluation with timing
async function getFlag(flagKey: string, userId: string): Promise<any> {
  const start = performance.now();
  const value = await posthog.getFeatureFlag(flagKey, userId);
  const durationMs = performance.now() - start;

  // Emit metrics to your monitoring system
  emitHistogram('posthog_flag_eval_duration_ms', durationMs, { flag: flagKey });
  emitCounter('posthog_flag_evals_total', 1, { flag: flagKey, result: String(value) });

  // Alert on slow evaluations (likely means local eval not configured)
  if (durationMs > 200) {
    console.warn(`[PostHog] Slow flag eval: ${flagKey} took ${durationMs.toFixed(0)}ms — check personalApiKey`);
  }

  return value;
}

// Example: emit to Prometheus via prom-client
import { Histogram, Counter, Gauge } from 'prom-client';

const flagDuration = new Histogram({
  name: 'posthog_flag_eval_duration_ms',
  help: 'PostHog feature flag evaluation duration',
  labelNames: ['flag'],
  buckets: [1, 5, 10, 50, 100, 200, 500, 1000],
});

const flagEvals = new Counter({
  name: 'posthog_flag_evals_total',
  help: 'Total PostHog feature flag evaluations',
  labelNames: ['flag', 'result'],
});

function emitHistogram(name: string, value: number, labels: Record<string, string>) {
  flagDuratio

PostHog Performance Tuning

Overview

Optimize PostHog for production workloads. The biggest performance wins are: local feature flag evaluation (eliminates network calls), proper batching configuration, event sampling for high-volume apps, and efficient HogQL queries with date filters.

Prerequisites

• posthog-node and/or posthog-js installed
• Personal API key (phx_...) for local flag evaluation
• Feature flags configured (if applicable)

Instructions

Step 1: Enable Local Feature Flag Evaluation

The single biggest performance improvement. Without local evaluation, every getFeatureFlag() call makes a network request (~50-200ms). With local evaluation, flag definitions are cached and evaluation is instant (~0.1ms).

import { PostHog } from 'posthog-node';

const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
  // This is the key: personal API key enables local flag evaluation
  personalApiKey: process.env.POSTHOG_PERSONAL_API_KEY,
  // Flag definitions are polled every 30 seconds by default
  // Adjust if you need faster flag updates:
  // featureFlagsPollingInterval: 10000, // 10 seconds
});

// With personalApiKey set, this evaluates locally (no network call)
const variant = await posthog.getFeatureFlag('pricing-experiment', 'user-123', {
  personProperties: { plan: 'pro', country: 'US' },
});

// Get all flags at once (still local, still fast)
const allFlags = await posthog.getAllFlags('user-123', {
  personProperties: { plan: 'pro' },
  groupProperties: { company: { industry: 'SaaS' } },
});

Step 2: Optimize Client Batching

// Production: batch events for network efficiency
const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
  flushAt: 20,           // Send batch when 20 events accumulated (default)
  flushInterval: 10000,  // Or flush every 10 seconds (default)
  requestTimeout: 10000, // 10 second timeout per request
  maxRetries: 3,         // Retry failed sends
});

// Serverless: flush immediately (function may exit)
const serverless = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
  flushAt: 1,       // Send every event immediately
  flushInterval: 0, // Don't wait
});

// CRITICAL: Always shutdown before process exits
process.on('SIGTERM', async () => {
  await posthog.shutdown();
  process.exit(0);
});

Step 3: Event Sampling (Browser)

import posthog from 'posthog-js';

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  api_host: 'https://us.i.posthog.com',
  before_send: (event) => {
  

PostHog Production Checklist

Overview

Production readiness verification for PostHog integrations. Covers SDK configuration hardening, graceful degradation when PostHog is unavailable, health check endpoints, proper shutdown hooks for serverless, and rollback procedures.

Prerequisites

• PostHog integration tested in staging
• Production PostHog project with phc_ key
• Personal API key (phx_) for server-side features
• Deployment pipeline configured

Instructions

Pre-Deployment Checklist

SDK Configuration:

• [ ] api_host set to correct region (us.i.posthog.com or eu.i.posthog.com)
• [ ] capture_pageview: false if using SPA with manual pageview tracking
• [ ] capture_pageleave: true for session duration accuracy
• [ ] Reverse proxy configured to bypass ad blockers (see posthog-sdk-patterns)
• [ ] posthog.debug() disabled in production (guarded by NODE_ENV)
• [ ] autocapture configured to exclude noisy elements

Server-Side:

• [ ] posthog.shutdown() called in SIGTERM handler and serverless function cleanup
• [ ] personalApiKey set for local flag evaluation (not just project key)
• [ ] flushAt and flushInterval tuned (default 20/10s is fine for most apps)

Security:

• [ ] Personal API key (phx) never in client bundles or NEXTPUBLIC_ vars
• [ ] .env files in .gitignore
• [ ] Separate PostHog project per environment

Step 1: Production SDK Configuration

// lib/posthog-production.ts
import { PostHog } from 'posthog-node';

const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: process.env.POSTHOG_HOST || 'https://us.i.posthog.com',
  personalApiKey: process.env.POSTHOG_PERSONAL_API_KEY,
  flushAt: 20,
  flushInterval: 10000,
  requestTimeout: 10000,
  maxRetries: 3,
});

// Graceful shutdown
async function shutdown() {
  await posthog.shutdown();
  process.exit(0);
}
process.on('SIGTERM', shutdown);
process.on('SIGINT', shutdown);

Step 2: Graceful Degradation

// PostHog should never break your app — wrap all calls
function safeCapture(distinctId: string, event: string, properties?: Record<string, any>) {
  try {
    posthog.capture({ distinctId, event, properties });
  } catch (error) {
    // Log but never throw — analytics should not crash your app
    console.error('[PostHog] Capture failed:', (error as Error).message);
  }
}

async function safeGetFlag(flagKey: string, userId

PostHog Rate Limits

Overview

PostHog rate limits apply to private API endpoints authenticated with a personal API key (phx_...). Public capture endpoints (/capture/, /batch/, /decide/) are not rate limited. Understanding which endpoints have limits is critical to avoiding 429 errors.

Prerequisites

• PostHog personal API key (phx_...) for admin endpoints
• Understanding of which endpoints you call and how often
• posthog-node or direct API usage

PostHog Rate Limit Tiers

Instructions

Step 1: Implement Exponential Backoff with Retry-After

async function postHogApiCall<T>(
  url: string,
  options: RequestInit,
  maxRetries = 5
): Promise<T> {
  for (let attempt = 0; attempt <= maxRetries; attempt++) {
    const response = await fetch(url, {
      ...options,
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${process.env.POSTHOG_PERSONAL_API_KEY}`,
        ...options.headers,
      },
    });

    if (response.ok) {
      return response.json();
    }

    if (response.status === 429) {
      // Honor the Retry-After header from PostHog
      const retryAfter = parseInt(response.headers.get('Retry-After') || '0');
      const backoffMs = retryAfter > 0
        ? retryAfter * 1000
        : Math.min(1000 * Math.pow(2, attempt) + Math.random() * 500, 32000);

      console.warn(`PostHog 429: retrying in ${Math.round(backoffMs)}ms (attempt ${attempt + 1}/${maxRetries})`);
      await new Promise(r => setTimeout(r, backoffMs));
      continue;
    }

    // Don't retry client errors (except 429)
    if (response.status >= 400 && response.status < 500) {
      const body = await response.text();
      throw new Error(`PostHog API ${response.status}

PostHog Reference Architecture

Overview

Production-grade architecture for PostHog analytics in a web application. Covers file structure, event taxonomy design, SDK initialization layers, feature flag management, group analytics for B2B, and data pipeline integration.

Prerequisites

• PostHog Cloud or self-hosted instance
• posthog-js and posthog-node SDKs
• Next.js or React application (patterns adapt to other frameworks)

Architecture

┌─────────────────────────────────────────────────────┐
│  Browser (posthog-js)                                │
│  $pageview, $autocapture, custom events, identify   │
│  Feature flag evaluation, session recordings         │
└────────────┬────────────────────────────────────────┘
             │ HTTPS (direct or reverse proxy)
             ▼
┌─────────────────────────────────────────────────────┐
│  PostHog Cloud (us.i.posthog.com)                    │
│  ┌──────────┐  ┌──────────┐  ┌───────────────────┐  │
│  │ Events   │  │ Feature  │  │ Session Replay    │  │
│  │ Pipeline │  │ Flags    │  │ & Recordings      │  │
│  └────┬─────┘  └────┬─────┘  └───────────────────┘  │
│       │              │                                │
│  ┌────┴──────────────┴────────────────────────────┐  │
│  │  Analytics: Trends, Funnels, Retention, Paths  │  │
│  │  HogQL (SQL), Dashboards, Cohorts              │  │
│  └────────────────────────────────────────────────┘  │
│  ┌────────────────────────────────────────────────┐  │
│  │  CDP: Destinations (Webhook, Slack, S3, etc.)  │  │
│  └────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────┘
             ▲
             │ posthog-node (server events, local flag eval)
┌────────────┴────────────────────────────────────────┐
│  Backend (API routes, webhooks, crons)               │
│  Server-side capture, group identify, flag eval      │
└─────────────────────────────────────────────────────┘

Instructions

Step 1: Project File Structure

src/
├── analytics/
│   ├── posthog.ts           # Browser SDK init (singleton)
│   ├── posthog-server.ts    # Server SDK init (singleton)
│   ├── events.ts            # Typed event constants
│   ├── flags.ts             # Feature flag key constants
│   └── hooks/
│       ├── useFeatureFlag.ts    # React hook for boolean flags
│       └── useExperiment.ts     # React hook for A/B variants
├── app/
│   ├── providers.tsx        # PostHogProvider wrapper
│   └── layout.tsx           # Root layout with provider
└── lib/
    └── analytics.ts         # High-level tracking functions

Step 2: Event Taxonomy

// analytics/events.ts
// Naming convention: object_action (noun_verb)
export const EVENTS = {
  // User lifecycle (track conversion funnel)
  USER_SIGNED_UP: 'user_signed_up',
  USER_LOGGE

PostHog SDK Patterns

Overview

Production-ready patterns for PostHog integrations: singleton client, type-safe event capture, React hooks for feature flags, Next.js App Router provider, and Python integration patterns.

Prerequisites

• posthog-js and/or posthog-node installed
• TypeScript project with strict mode
• React/Next.js (for frontend patterns)

Instructions

Step 1: Singleton Server Client

// lib/posthog-server.ts
import { PostHog } from 'posthog-node';

let client: PostHog | null = null;

export function getPostHogServer(): PostHog {
  if (!client) {
    client = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
      host: process.env.POSTHOG_HOST || 'https://us.i.posthog.com',
      personalApiKey: process.env.POSTHOG_PERSONAL_API_KEY,
      flushAt: 20,
      flushInterval: 10000,
    });
  }
  return client;
}

// Graceful shutdown hook
process.on('SIGTERM', async () => {
  if (client) await client.shutdown();
  process.exit(0);
});

Step 2: Type-Safe Event Capture

// lib/analytics/events.ts
type EventMap = {
  user_signed_up: { method: 'email' | 'google' | 'github' };
  feature_used: { feature_name: string; duration_ms?: number };
  subscription_started: { plan: string; interval: 'monthly' | 'annual'; mrr: number };
  item_created: { item_type: string; source: 'web' | 'api' };
  search_performed: { query: string; results_count: number };
};

export function capture<K extends keyof EventMap>(
  distinctId: string,
  event: K,
  properties: EventMap[K]
) {
  const ph = getPostHogServer();
  ph.capture({ distinctId, event, properties });
}

// Usage: fully type-checked
capture('user-123', 'subscription_started', {
  plan: 'pro',
  interval: 'annual',
  mrr: 99,
});

Step 3: React Feature Flag Hook

// hooks/useFeatureFlag.ts
'use client';
import { useEffect, useState } from 'react';
import posthog from 'posthog-js';

export function useFeatureFlag(flagKey: string): boolean | undefined {
  const [enabled, setEnabled] = useState<boolean | undefined>(undefined);

  useEffect(() => {
    // Check immediately if flags are already loaded
    const current = posthog.isFeatureEnabled(flagKey);
    if (current !== undefined) {
      setEnabled(current);
    }

    // Listen for flag updates (initial load or remote changes)
    posthog.onFeatureFlags(() => {
      setEnabled(posthog.isFeatureEnabled(flagKey) ?? false);
    });
  }, [flagKey]);

  return enabled;
}

// Multivariate variant hook
export function useFeatureFlagVariant(flagKey: string): string | undefined {
  const [variant, setVariant] = useState<string | undefined>(unde

PostHog Security Basics

Overview

Secure PostHog API key management, least-privilege access, and secret rotation. PostHog has two key types with very different security profiles: the Project API Key (phc...) is intentionally public and safe to include in frontend bundles, while the Personal API Key (phx...) grants admin access and must never be exposed.

Prerequisites

• PostHog account with admin access
• Understanding of environment variable management
• .gitignore configured

Instructions

Step 1: Understand Key Security Profiles

# .env (NEVER commit)
NEXT_PUBLIC_POSTHOG_KEY=phc_abc123   # Safe for frontend (NEXT_PUBLIC_ prefix)
POSTHOG_PERSONAL_API_KEY=phx_xyz789  # Server-only — NEVER in frontend code
POSTHOG_PROJECT_ID=12345

# .gitignore
.env
.env.local
.env.*.local

Step 2: Create Scoped Personal API Keys

set -euo pipefail
# Create a read-only key for BI dashboards
curl -X POST "https://app.posthog.com/api/personal_api_keys/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "label": "bi-dashboard-readonly",
    "scopes": ["insight:read", "dashboard:read", "query:read"]
  }'

# Create a key scoped to feature flags only
curl -X POST "https://app.posthog.com/api/personal_api_keys/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "label": "feature-flag-service",
    "scopes": ["feature_flag:read", "feature_flag:write"]
  }'

Step 3: Rotate Personal API Keys

set -euo pipefail
# 1. Create new key in PostHog Settings > Personal API Keys
# 2. Update secret in your deployment platform
# Vercel:
vercel env rm POSTHOG_PERSONAL_API_KEY production
vercel env add POSTHOG_PERSONAL_API_KEY production

# GitHub Actions:
gh secret set POSTHOG_PERSONAL_API_KEY --body "phx_new_key_here"

# 3. Verify new key works
curl -s "https://app.posthog.com/api/projects/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" | jq '.[0].name'

# 4. Delete old key in PostHog dashboard