FlowIndex

FlowIndex is a full-stack blockchain explorer and indexer purpose-built for the Flow blockchain. It provides real-time block ingestion, comprehensive historical backfill, a rich REST API, WebSocket live updates, and a modern frontend UI.

Core Features

• Real-time block indexing -- A forward ingester tracks the chain head and indexes new blocks within seconds of finalization.
• Historical backfill -- A backward ingester fills the complete chain history, with spork-aware node routing for seamless cross-spork coverage.
• Flow-EVM support -- Automatic detection and indexing of EVM transactions embedded in Flow, including EVM hash mapping, sender/receiver extraction, and gas tracking.
• WebSocket live updates -- Frontend clients receive new blocks and transactions in real time via a WebSocket broadcast hub.
• REST API -- A comprehensive API covering blocks, transactions, accounts, fungible tokens, NFTs, contracts, staking, DeFi, and analytics.
• 17+ background workers -- Specialized processors derive token transfers, NFT ownership, account metadata, staking events, DeFi swaps, daily statistics, and more.
• Cursor-based pagination -- All list endpoints use efficient cursor pagination to avoid expensive offset scans.
• Partitioned storage -- Raw blockchain data is stored in PostgreSQL range-partitioned tables for scalable querying at terabyte scale.

Tech Stack

Architecture at a Glance

flowchart LR
  FAN["Flow Access Nodes"] --> FI["Forward Ingester"]
  FAN --> BI["Backward Ingester"]
  FI --> DB["PostgreSQL"]
  BI --> DB
  DB --> W["Workers & Derivers"]
  W --> DB
  DB --> API["REST API + WebSocket"]
  API --> FE["Frontend UI"]

The system follows a dual ingester + deriver pattern:

1. Ingesters fetch raw blocks, transactions, and events from Flow Access Nodes and store them in partitioned raw.* tables.
2. Derivers and workers read raw data and produce derived tables in app.* -- token transfers, account metadata, NFT ownership, staking state, and more.
3. The API server queries both raw and app tables to serve the frontend and external consumers.

See the Architecture page for a detailed breakdown.

Project Structure

backend/         Go indexer + API server
frontend/        TanStack Start SSR app (React 19, TypeScript)
supabase/        Self-hosted Supabase auth stack
devportal/       Developer portal (Fumadocs + Scalar)
scripts/         Utility scripts

Next Steps

• Getting Started -- Run FlowIndex locally with Docker Compose
• Architecture -- Understand the ingestion pipeline and worker system
• API Reference -- Explore REST endpoints and WebSocket events
• Configuration -- Environment variables reference
• EVM Support -- How Flow-EVM transactions are indexed