My project requirement is bot has to be stateless.
There is one loan based broker web application where user will process the initial Disclosure and then bot has to login to lender application and need search the loan number, identify any workflow rules or fatal error is there, if there is errors need to extract that error and notify to user and close the application.
If No errors preview documents should be downloaded and notify user about preview initial disclosure completion.
How this can be achieved using API request and respond back through that same API
Is this possible without using Queue/Orchestrator/Excel for data
Interesting use case you have there. Think of UiPath as a web application, you can send and receive data and also trigger actions like start a job, add queue items, modify schedules, etc. I recommend you read the api documentation to come up with the best architecture that meets your needs. You can make api calls from UiPath using the WebAPI.Activities library
Regarding your data storage, what are you exactly trying to accomplish? a few points below:
Orchestrator is mandatory, it hold your licenses and provides services to your bots, also hosts the API
A queue more than data storage works exactly as that a queue of your transactions, (considering your automation process is transactional)
You can use several data sources other than excel, examples are: SQL and NoSQL databases, UiPath’s Data services, csv files, JSON documents, OLEDB, ODBC you just need to put together a reliable design