# 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.**