subql

SubQuery is an open source data indexing framework for blockchain (web3) applications. The core problem it solves is that blockchains store raw transaction and event data in a format that is very hard to query — if your app needs to ask questions like "show me all NFT transfers for this wallet" or "what happened to this smart contract over the past week," you can't just run a SQL query against the chain. SubQuery sits between the blockchain and your app: it reads raw on-chain data, processes it according to rules you define, stores it in a PostgreSQL database, and exposes it through a standard GraphQL API that your frontend can query quickly.

It supports a wide range of blockchains including Polkadot, Ethereum and EVM-compatible networks, Cosmos, Algorand, NEAR, Stellar, Solana, Starknet, and others, and you can even index data across multiple chains at once. You define what data to capture using a project manifest and TypeScript mapping functions, then run the SubQuery indexer node alongside a GraphQL query service. Projects can be run locally for development, self-hosted on your own infrastructure, or published to the decentralized SubQuery Network where others host your indexer for you.

You would use SubQuery if you are building a decentralized app — such as a DeFi dashboard, an NFT explorer, or a governance tool — and need reliable, fast access to historical and real-time blockchain data without building your own data pipeline from scratch.