# Data indexing service

Because there's no server, every data of a DApp will be stored on blockchain. And keeping track of all those datas is too complicated if getting data directly from blockchain.

To solve this, DApp's developers need to use a data indexing service, such as [The Graph](https://thegraph.com/docs/en/about/introduction/).

The Graph is a decentralized protocol for indexing and querying data from blockchains, starting with Ethereum. It makes it possible to query data that is difficult to query directly. Luckily, The Graph open-sourced their source code and build a Docker image so that every developers can run their own graph on any EVM-compatible network.

To start running your graph node:

1. Download the `docker-compose.yml` file from [The Graph's public repo](https://github.com/graphprotocol/graph-node/blob/master/docker/docker-compose.yml). 
2. Edit `ethereum` field to **`mainnet:https://rpc.kardiachain.io`**
3. Run **`docker-compose up -d`**

After that, a GraphQL playground will be served on port **8000.**


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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.kardiachain.io/docs/archived-docs/tutorials/building-dapp/data-indexing-service.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.