# Using The Graph

### Introduction <a href="#introduction" id="introduction"></a>

Indexing an application provides more efficient access to its organizational information. For example, search engines index the entire Internet, and you can search for information more easily through it

Indexing blockchain data is really, really hard.Blockchain properties like finality, chain reorganizations, or uncled blocks complicate this process further, and make it not just time consuming but conceptually hard to retrieve correct query results from blockchain data.

&#x20;In addition, developers can build APIs (indexed "subgraphs") can used to query data specific to a set of smart contracts. Data is fetched with a standard GraphQL API. You can visit The Graph's documentation site to read more [about The Graph protocol](https://thegraph.com/docs/about/introduction#what-the-graph-is).

Due to the support of Ethereum tracing modules in REI network, The Graph is capable of indexing blockchain data in REI. This guide takes you through the creation of a simple subgraph for a Bank contract on testnet. This guide can be adapted for mainnet.


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# 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.rei.network/developer/guides/using-the-graph.md?ask=<question>
```

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.