ADR 011: Product Analytics

Context

The monorepo includes a Next.js web app (apps/web) and an Expo mobile app (apps/mobile). We need product analytics to:

• Track usage across web and mobile (events, page views, feature adoption)
• Analyze behavior via funnels, retention, cohorts, user paths
• Support product decisions with data-driven insights
• Optionally use session replay, feature flags, and experiments
• Respect privacy with EU/US regions and optional self-hosting
• Stay within budget with a generous free tier or predictable costs

We currently use @vercel/analytics for basic web analytics only; it does not provide product-level metrics or cross-app coverage.

Considered Options

Option A – PostHog (Chosen)

Full product analytics platform with web and mobile SDKs. Cloud or self-hosted.

Pros

• Multi-platform: Official SDKs for Next.js and Expo/React Native
• Generous free tier: 1M events, 5K recordings, 1M feature-flag requests per month
• All-in-one: Product analytics, session replay, feature flags, experiments, surveys
• Open source: MIT license, transparent, no vendor lock-in
• Cloud or self-host: Start free on Cloud; self-host when needed
• Large ecosystem: 30k+ GitHub stars, active development, strong docs
• Usage-based pricing: Pay only beyond free limits; billing caps available

Cons

• Heavier SDK (~52 KB) vs lightweight alternatives
• Self-hosting requires multiple services (ClickHouse, Kafka, Redis, PostgreSQL)
• Paid-plan features (e.g. advanced experiments) are Cloud-only when self-hosting

Option B – OpenPanel

Lightweight, analytics-focused open source alternative to Mixpanel.

Pros

• Lightweight SDK: ~2.3 KB vs PostHog’s ~52 KB
• Simpler self-host: Single Docker container
• Cookie-free by default: No consent banners needed
• Focused analytics: Funnels, cohorts, retention, user profiles

Cons

• Newer, smaller community and ecosystem
• No feature flags, session replay, or experiments
• Less mature mobile support than PostHog

Option C – Trench

Infrastructure for custom analytics dashboards (ClickHouse, Kafka, Node.js).

Pros

• Flexible pipeline for custom dashboards
• Full control over storage and processing

Cons

• No out-of-the-box product analytics; requires significant build work
• Not suited for rapid adoption

Option D – Google Analytics / Mixpanel (Proprietary)

Third-party hosted analytics.

Pros

• Widely used, mature tooling

Cons

• Vendor lock-in, privacy concerns, opaque pricing
• Does not align with our preference for open source and portability

Decision

We adopt PostHog for product analytics across web and mobile.

TLDR: Comparison Table

Main reasons:

• Multi-platform coverage (Next.js + Expo) with first-class SDKs
• Generous free tier; most teams stay at $0
• All-in-one: analytics, replay, flags, experiments in one place
• Open source and self-hostable when needed
• Strong community and documentation

Cloud vs Self-Host

• Start with PostHog Cloud: No setup, free tier, US/EU regions, GDPR support
• Self-host when required: Data residency, compliance, or cost at high scale
• Self-host requirements: ~4 vCPU, 16 GB RAM, 30+ GB storage; Docker Compose stack (PostHog, ClickHouse, Kafka, Redis, PostgreSQL, MinIO, Caddy)

Integration Approach

• Web: posthog-js (or posthog-node), deferred load via next/dynamic
• Mobile: posthog-react-native with PostHogProvider
• Events: Page/screen views (auto), key actions (signup, feature usage), custom properties for segmentation

Related Documentation

• Product Analytics - Setup, pricing, and integration details
• ADR 001: Monorepo - Turborepo and multi-app structure
• Logging - Server/client logging (distinct from product analytics)