Blockchain indexers

A blockchain indexer is infrastructure that reads raw chain events, parses them against known contract ABIs, and stores the result in a queryable database — basically, it turns the blockchain back into something you can do normal SQL or GraphQL queries against. Asking a node directly for "all trades by this wallet on Uniswap last month" is painfully slow; indexers make it instant. The category leaders: The Graph is the decentralised one, with a protocol of indexers, curators, and delegators around "subgraphs" you deploy; Ponder and Envio are TypeScript-first, developer-friendly indexers you self-host, optimised for speed and DX. Every non-trivial DApp uses one — the frontend doesn't talk to the chain directly for historical data, it talks to an indexer.