# How to Vibe Code Your Own Fullstory (and Stop Paying for It)

> Intelligent Digital Experience Platform: AI-Powered Behavioral Analytics

- Site: https://fullstory.com
- Category: Digital Experience Analytics
- Platforms: Web app
- Verdict: **Serious undertaking** (42/100 vibecodeable)
- Estimated effort: 6-8 weeks of intensive engineering

## Verdict

You can build a single-user subset with session replay and basic event metrics, but ingestion scale and DOM mutation performance make it a serious undertaking.

Fullstory processes billions of high-frequency DOM mutation events with custom compression algorithms and complex analytical indexing. While an AI agent can scaffold a Next.js dashboard and a basic MutationObserver recording script, handling cross-browser DOM serialization edge cases, memory leaks in long-running recordings, and real-time event analytics will consume weeks of intense debugging. This is an engineering feat, not a weekend wrapper.

### What you can't replicate

- Billions of historical cross-industry behavioral sessions
- Enterprise-grade compliance guarantees and automated PII scrubbing at scale
- Native integrations across thousands of third-party enterprise tools

## What it does

Behavioral data analytics platform combining session replay, autocapture, product analytics, and AI-driven insights.

### Core features

- Client-side mutation observer & DOM event recording
- Session replay player with timeline scrubber
- Click heatmaps and rage-click detection
- Product analytics (funnels, retention, path analysis)
- Privacy masking engine for PII and sensitive inputs
- Event ingestion pipeline and columnar storage

## The business

### Pricing

- FullstoryFree: Free — For individuals and small teams
- Business, Advanced & Enterprise: Custom — Tiered enterprise packages based on volume and add-ons

### Funding

$196M raised.
- Seed (2014)
- Series A ($10M, 2015)
- Series B ($15M, 2017)
- Series C ($32M, 2019)
- Series D (~$103M at $1.8B valuation, 2021)
- Venture Tranche ($25M, 2022)
Investors: Permira, Google Ventures (GV), Kleiner Perkins, Salesforce Ventures, Stripes, Glynn Capital

Founded 2014.
Team size: ~570.

## The hard parts

- Building a lightweight client-side recording script that serializes DOM mutations without lagging the host application
- Designing a high-throughput event ingestion and indexing pipeline for massive JSON event payloads
- Implementing bulletproof client-side data masking for passwords and PII to maintain legal compliance
- Computing dynamic funnel queries and conversion paths over large time-series event stores

## How to vibe code Fullstory

### Prerequisites

- Node.js (free): Required for running the Next.js development environment and build tools.
- GitHub (free): Source code control and deployment pipeline integration.

### Recommended AI tools

- Claude Code: Best-in-class coding agent for scaffolding complex full-stack pipelines, ingestion handlers, and UI dashboards.
- Cursor: Essential for iterative UI development, reviewing session player components, and inspecting complex React code.

### Stack

- Frontend: Next.js with Tailwind CSS, Lucide icons, and rrweb for session recording playback
- Backend: Next.js API Routes / Server Actions for event ingestion and analytics aggregation
- Database: ClickHouse Cloud for high-throughput time-series event storage, backed by Neon Postgres for user accounts
- Auth: better-auth for self-hosted TypeScript authentication
- Payments: Stripe
- Other: Cloudflare R2 for storing compressed session recording chunks, PostHog for product analytics telemetry

### Hosting

- Vercel (Hosting the Next.js frontend and dashboard application): $0-20/mo
- ClickHouse (High-performance columnar storage for event streams and analytics queries): $0-50/mo
- Cloudflare (R2 object storage for session recording chunks): $0-5/mo

### Build guide

1. **Project Scaffolding and Database Schema** — Initialize the Next.js application with Tailwind CSS, configure better-auth with Neon Postgres, and establish ClickHouse tables for high-volume event ingestion.

```
Initialize a new Next.js project with TypeScript, Tailwind CSS, and App Router. Set up better-auth for user authentication using Neon Postgres as the primary relational store. Create a database migration script for projects, user sessions, and organization settings. Add ClickHouse client configuration for storing high-volume event streams with schema fields: event_id, session_id, user_id, event_type, timestamp, target_selector, and payload JSON.
```

2. **Client-Side Tracking and Recording SDK** — Develop a lightweight client-side JavaScript snippet using rrweb or custom mutation observers to autocapture DOM mutations, clicks, inputs, and console errors.

```
Build a lightweight client-side tracking script (SDK) written in TypeScript that can be injected into target web apps. Implement rrweb or an optimized MutationObserver to capture DOM snapshots, DOM mutations, mouse movements, clicks, scrolls, and rage clicks. Ensure sensitive form inputs (passwords, credit card fields) are masked automatically using CSS selectors or attributes. Batch recorded events in memory and flush them via navigator.sendBeacon or compressed POST requests to our ingestion endpoint every 5 seconds.
```

3. **High-Throughput Ingestion API Pipeline** — Build a robust backend ingestion endpoint in Next.js that validates incoming event payloads, buffers bursts, and writes them efficiently to ClickHouse and Cloudflare R2.

```
Create a high-performance API endpoint `/api/v1/collect` in Next.js that accepts batch event payloads from our tracking SDK. Implement request validation, rate limiting, and deduplication. Write raw event streams asynchronously into ClickHouse, and aggregate large session DOM recording chunks into Cloudflare R2 object storage with compressed zlib format. Handle CORS headers securely to allow cross-origin tracking requests from client applications.
```

4. **Session Replay Player Dashboard** — Build an interactive session replay dashboard featuring a timeline scrubber, playback speed controls, event log inspector, and DOM player canvas.

```
Develop a session replay player page in the Next.js frontend using rrweb-player or a custom canvas renderer. Fetch session metadata from Postgres and replay chunks from Cloudflare R2. Build UI controls for play, pause, variable speed (1x-8x), timeline scrubbing, and skip-inactivity. Create a side panel displaying synchronous console logs, network requests, and user interaction events indexed by timestamp during the session.
```

5. **Product Analytics and Funnel Queries** — Implement product analytics views including event trends, user segmentation filters, and conversion funnel step analysis backed by ClickHouse queries.

```
Create a product analytics dashboard featuring custom charts (bar charts, line graphs) for event frequency and user trends over time. Implement a conversion funnel query builder where product managers can define ordered event steps (e.g., Page Viewed -> Add to Cart -> Checkout Completed) and compute conversion drop-off percentages using ClickHouse window functions and aggregations. Ensure filters for date ranges and user segments are fully interactive.
```

6. **Heatmaps and Rage Click Detection** — Build visual click heatmaps and aggregation layers to highlight user friction points and rage-click clusters on recorded pages.

```
Build a heatmap visualization module that fetches click and interaction coordinates for a specific URL path from ClickHouse. Render an overlay canvas on top of a wireframe or snapshot of the target page, displaying click density heat spots and highlighting clusters classified as 'rage clicks' (rapid repeated clicks in a tight bounding box). Include filtering by device type and date.
```

7. **Polish, Error Handling, and Testing** — Conduct end-to-end testing, optimize SDK payload sizes, secure database connection pools, and polish the dashboard UI for production deployment.

```
Perform a comprehensive review of the tracking SDK and dashboard application. Optimize ClickHouse indexing for fast session lookups and funnel aggregations. Implement error boundary handling across all dashboard views, add loading skeletons for asynchronous analytics queries, and ensure responsive layout design across desktop viewports. Write integration tests for the event collection and replay pipeline.
```

### Cost vs paying

**Starting costs (one-time):**

- Domain name: $12
- Total: ~$12 one-time

**Ongoing costs (monthly):**

- Vercel Hobby/Pro: $20/mo
- ClickHouse Cloud: $25/mo
- Cloudflare R2: $5/mo
- Total: ~$50/mo

- Paying for the SaaS instead: $Custom / Enterprise
- Build time: 80-120 hours
- AI tool credits: $20/mo (Claude Pro / Cursor)
- Break-even: N/A (Personal clone)

## Sources

- [Fullstory Official Website](https://fullstory.com)
- [Fullstory Plans and Pricing](https://fullstory.com/pricing)
- [Crunchbase Fullstory Profile](https://www.crunchbase.com/organization/fullstory)