> For the complete documentation index, see [llms.txt](https://docs.envio.dev/llms.txt).
## Introduction
In this tutorial, you'll learn how to index ERC20 token transfers on the Base network using Envio HyperIndex. By leveraging the no-code [contract import](https://docs.envio.dev/docs/HyperIndex/contract-import) feature, you'll be able to quickly analyze USDC transfer activity, including identifying the largest transfers.
We'll create an indexer that tracks all USDC token transfers on Base by extracting the `Transfer` events emitted by the USDC contract. The entire process takes less than 5 minutes to set up and start querying data.
## Prerequisites
Before starting, ensure you have the following installed:
- **[Node.js](https://nodejs.org/en/download/current)** _(v22 or newer recommended)_
- **[pnpm](https://pnpm.io/installation)** _(v8 or newer)_
- **[Docker Desktop](https://www.docker.com/products/docker-desktop/)** _(required to run the Envio indexer locally)_
> **Note:** Docker is specifically required to run your blockchain indexer locally. You can skip Docker installation if you plan only to use Envio Cloud.
## Step 1: Initialize Your Indexer
1. Open your terminal in an empty directory and run:
```bash
pnpx envio@2 init
```
2. Name your indexer (we'll use "usdc-base-transfer-indexer" in this example):
3. Choose your preferred language (TypeScript, JavaScript, or ReScript):
## Step 2: Import the USDC Token Contract
1. Select **Contract Import** → **Block Explorer** → **Base**
2. Enter the USDC token contract address on Base:
```
0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
```
[View on BaseScan](https://basescan.org/address/0x833589fcd6edb6e08f4c7c32d4f71b54bda02913)
3. Select the `Transfer` event:
- Navigate using arrow keys (↑↓)
- Press spacebar to select the event
> **Tip:** You can select multiple events to index simultaneously if needed.
4. When finished adding contracts, select **I'm finished**
## Step 3: Start Your Indexer
1. If you have any running indexers, stop them first:
```bash
pnpm envio stop
```
> **Note:** You can skip this step if this is your first time running an indexer.
2. Start your new indexer:
```bash
pnpm dev
```
This command:
- Starts the required Docker containers
- Sets up your database
- Launches the indexing process
- Opens the Hasura GraphQL interface
## Step 4: Understanding the Generated Code
Let's examine the key files that Envio generated:
### 1. `config.yaml`
This configuration file defines:
- Network to index (Base)
- Starting block for indexing
- Contract address and ABI details
- Events to track (Transfer)
### 2. `schema.graphql`
This schema defines the data structures for the Transfer event:
- Entity types based on event data
- Field types for sender, receiver, and amount
- Any relationships between entities
### 3. `src/EventHandlers.*`
This file contains the business logic for processing events:
- Functions that execute when Transfer events are detected
- Data transformation and storage logic
- Entity creation and relationship management
## Step 5: Exploring Your Indexed Data
Now you can interact with your indexed USDC transfer data:
### Accessing Hasura
1. Open Hasura at [http://localhost:8080](http://localhost:8080)
2. When prompted, enter the admin password: `testing`
### Monitoring Indexing Progress
1. Click the **Data** tab in the top navigation
2. Find the `_events_sync_state` table to check indexing progress
3. Observe which blocks are currently being processed
> **Note:** Thanks to Envio's [HyperSync](https://docs.envio.dev/docs/hypersync), you can index millions of USDC transfers in just minutes rather than hours or days with traditional methods.
### Querying Indexed Events
1. Click the **API** tab
2. Construct a GraphQL query to explore your data
Here's an example query to fetch the 10 largest USDC transfers:
```graphql
query LargestTransfers {
FiatTokenV2_2_Transfer(limit: 10, order_by: { value: desc }) {
from
to
value
blockTimestamp
}
}
```
3. Click the **Play** button to execute your query
## Conclusion
Congratulations! You've successfully created an indexer for USDC token transfers on Base. In just a few minutes, you've indexed over 3.6 million transfer events and can now query this data in real-time.
### What You've Learned
- How to initialize an indexer using Envio's contract import feature
- How to index ERC20 token transfers on the Base network
- How to query and analyze token transfer data using GraphQL
### Next Steps
- Try customizing the event handlers to add additional logic
- Create aggregated statistics about token transfers
- Add more tokens or events to your indexer
- Deploy your indexer to Envio Cloud
For more tutorials and advanced features, check out our [documentation](https://docs.envio.dev) or watch our [video walkthrough](https://www.youtube.com/watch?v=e1xznmKBLa8) on YouTube.
3. Choose your preferred language (TypeScript, JavaScript, or ReScript):
## Step 2: Import the USDC Token Contract
1. Select **Contract Import** → **Block Explorer** → **Base**
2. Enter the USDC token contract address on Base:
```
0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
```
[View on BaseScan](https://basescan.org/address/0x833589fcd6edb6e08f4c7c32d4f71b54bda02913)
3. Select the `Transfer` event:
- Navigate using arrow keys (↑↓)
- Press spacebar to select the event
> **Tip:** You can select multiple events to index simultaneously if needed.
4. When finished adding contracts, select **I'm finished**
## Step 3: Start Your Indexer
1. If you have any running indexers, stop them first:
```bash
pnpm envio stop
```
> **Note:** You can skip this step if this is your first time running an indexer.
2. Start your new indexer:
```bash
pnpm dev
```
This command:
- Starts the required Docker containers
- Sets up your database
- Launches the indexing process
- Opens the Hasura GraphQL interface
## Step 4: Understanding the Generated Code
Let's examine the key files that Envio generated:
### 1. `config.yaml`
This configuration file defines:
- Network to index (Base)
- Starting block for indexing
- Contract address and ABI details
- Events to track (Transfer)
### 2. `schema.graphql`
This schema defines the data structures for the Transfer event:
- Entity types based on event data
- Field types for sender, receiver, and amount
- Any relationships between entities
### 3. `src/EventHandlers.*`
This file contains the business logic for processing events:
- Functions that execute when Transfer events are detected
- Data transformation and storage logic
- Entity creation and relationship management
## Step 5: Exploring Your Indexed Data
Now you can interact with your indexed USDC transfer data:
### Accessing Hasura
1. Open Hasura at [http://localhost:8080](http://localhost:8080)
2. When prompted, enter the admin password: `testing`
### Monitoring Indexing Progress
1. Click the **Data** tab in the top navigation
2. Find the `_events_sync_state` table to check indexing progress
3. Observe which blocks are currently being processed
> **Note:** Thanks to Envio's [HyperSync](https://docs.envio.dev/docs/hypersync), you can index millions of USDC transfers in just minutes rather than hours or days with traditional methods.
### Querying Indexed Events
1. Click the **API** tab
2. Construct a GraphQL query to explore your data
Here's an example query to fetch the 10 largest USDC transfers:
```graphql
query LargestTransfers {
FiatTokenV2_2_Transfer(limit: 10, order_by: { value: desc }) {
from
to
value
blockTimestamp
}
}
```
3. Click the **Play** button to execute your query
## Conclusion
Congratulations! You've successfully created an indexer for USDC token transfers on Base. In just a few minutes, you've indexed over 3.6 million transfer events and can now query this data in real-time.
### What You've Learned
- How to initialize an indexer using Envio's contract import feature
- How to index ERC20 token transfers on the Base network
- How to query and analyze token transfer data using GraphQL
### Next Steps
- Try customizing the event handlers to add additional logic
- Create aggregated statistics about token transfers
- Add more tokens or events to your indexer
- Deploy your indexer to Envio Cloud
For more tutorials and advanced features, check out our [documentation](https://docs.envio.dev) or watch our [video walkthrough](https://www.youtube.com/watch?v=e1xznmKBLa8) on YouTube.