# Chain Indexing Retrieving historical data on a smart contract can be frustrating when building a dapp. Fortunately, several decentralized indexing infrastructures offer easy ways to query smart contract data through APIs. This section will guide you through the available options on IoTeX, including our official Analytics API service. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.iotex.io/blockchain/build/web3-development/chain-indexing.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.