Amazon Textract reads documents such as forms, invoices and multipage PDFs and returns the text and structure it finds. Large and multipage documents go through its asynchronous APIs.
A customer puts a document in Amazon S3 and calls a start operation like StartDocumentAnalysis. Textract returns a job ID straight away, does the work in the background, and publishes a completion notice to an Amazon SNS topic. The customer then fetches the results with the matching get operation, such as GetDocumentAnalysis.
That simple contract hides a lot. Every document a customer sends has to be picked up, processed and accounted for, whatever the traffic looks like.