# Use Cases
source: https://developer.mastercard.com/doconomy-aland-index/documentation/use-cases/index.md

This section provides sample use cases for implementing your solution using the Doconomy Aland Index API. The user experience can be designed as required.
Note: To experience the API in a Sandbox environment, refer to the [API Reference](https://developer.mastercard.com/doconomy-aland-index/documentation/api-reference/index.md) section. You can execute the API with request parameters of your choice and analyze the response.

## Supported Currencies and Merchant Categories {#supported-currencies-and-merchant-categories}

These are support APIs that should be used to fetch the list of supported currencies and MCCs. This data should be used for transaction filtering before calling the `/transaction-footprints` API.
Note:   

* Merchant Category Codes (MCCs) is an assigned **fixed four-digit numeric** values as per the **ISO8583** that identifies a merchant's primary business. Customers must include a valid MCC in all transaction requests for successful carbon scoring.
* Supported Currency Codes are **fixed three letters** as per the **ISO4217** . Numeric representation of currency codes are **not supported** as of now.
Tip: As we are continuously working towards supporting more currencies and MCCs, this data should be cached and refreshed every 24-hours.

The sequence diagram shows the order of events for a solution that uses `/supported-currencies` and `/supported-merchant-categories` APIs.
Diagram supported-currencies

### Supported Currencies API {#supported-currencies-api}


API Reference: `GET /supported-currencies`

### Supported Merchant Categories API {#supported-merchant-categories-api}


API Reference: `GET /supported-merchant-categories`

## Transaction Footprints {#transaction-footprints}

You can create apps to let consumers view their carbon impact on the environment based on their spending habits, both in real-time and historical transactions.
You can also supplement this use case with additional insights for your consumers. For example, providing real-time notification of carbon score, providing weekly and monthly carbon score or providing a weekly comparison of carbon score and letting consumers know if they need to take an action.

The sample app shows how consumers view their carbon impact.
![Carbon Score](https://static.developer.mastercard.com/content/doconomy-aland-index/Images/usecases/CarbonScore.png) ![TransactionCarbonScore](https://static.developer.mastercard.com/content/doconomy-aland-index/Images/usecases/TxCarbonScore.png) ![MonthlyCarbonScore](https://static.developer.mastercard.com/content/doconomy-aland-index/Images/usecases/MonthlyCarbonScore.png)

The sequence diagram shows the order of events for a solution that uses the `/transaction-footprints` API.

Diagram carbon-impact-diagram

**The sequence of steps for this operation:**

1. Consumer requests to view his carbon impact from the Issuer app.
2. The issuer app sends a request to the Issuer server to calculate the carbon score.
3. The issuer server fetches the transaction history of the consumer from the system.
4. The issuer server filters the transactions based on supported currencies and MCCs and sends the filtered transactions as a request parameter while calling the POST `/transaction-footprints` API.
5. Doconomy Aland Index validates the request, calculates, and returns the carbon footprints along with carbon and water social costs for each transaction.
6. Issuer server compliments the carbon score along with actionable insights and returns to Issuer app.
7. Issuer app displays Consumers' carbon impact along with actionable insights.

<br />

You will receive an error response for any invalid or missing request parameter. More information about the error codes is available [here](https://developer.mastercard.com/doconomy-aland-index/documentation/code-and-formats/index.md).

### Transaction Footprints API {#transaction-footprints-api}


API Reference: `GET /transaction-footprints`

## Next Steps {#next-steps}

Now that you have an understanding of the different use cases the service uses, proceed to the [API Reference](https://developer.mastercard.com/doconomy-aland-index/documentation/api-reference/index.md) section to interact with all of our endpoints on the API explorer.