Querying Appian database

Yes you can expose Appian data through WebApi's . Use query templates (Either data type or Record) to get the data 
https://docs.appian.com/suite/help/24.3/Designing_Web_APIs.html

Hello [mention:2b8447070abf417b81f606c8ef1d5bf8:e9ed411860ed4f2ba0265705b8793d05] , 

Yes, we can query the data. There are multiple methods available for retrieving the data, including web APIs, imports, CDT and records. Each method is suitable for different query requirements.

• Web APIs: If you're dealing with real-time data or integrating with third-party systems, we would use web APIs to fetch the data dynamically.

• Import: If you have large datasets that need to be imported into your system, we can use imports (such as CSV or other file formats) to bring the data in efficiently.

• CDT: This approach is useful when working with standardized data structures that can be easily integrated and manipulated consistently.

• Records: When working within a specific platform, such as a CRM or database, records are the best way to interact with and we can easily organize the data.

If you are creating a record object to fetch the data into Appian, the you can use that record to create a webApi easily. You would need a service account to authorize and authenticate that WebAPI

Appian has an object called Web API specifically designed for this case. You can create a rule to query the data in Appian and expose the result of query using web API as a HTTP response. Which will be response to your KPI application's HTTP request.