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# Apollo Client

#### Apollo Client Creation

The Apollo Client is set up using the GraphQL server's URI and the client's cache is configured.

```typescript
typescriptCopy codeimport { ApolloClient, InMemoryCache } from "@apollo/client/core/index.js";
import { HttpLink } from "@apollo/client/link/http/HttpLink.js";

export function createApolloClient(uri: string) {
  return new ApolloClient({
    link: new HttpLink({
      uri,
    }),
    ssrMode: typeof window === "undefined",
    connectToDevTools:
      typeof window !== "undefined" && process.env.NODE_ENV === "development",
    cache: new InMemoryCache(),
  });
}
```

* **uri**: The endpoint of your GraphQL server.
* **ssrMode**: Configures the client for server-side rendering if the code is running on the server.
* **connectToDevTools**: Enables connection to browser development tools in development mode.
* **cache**: Configures the client to use an in-memory cache for storing query results.

#### Fetching Data

To fetch data specific to a blockchain network (e.g., Polygon or BSC), the appropriate GraphQL subgraph URI is determined based on the network chain ID. Then the Apollo Client executes a query to the subgraph.