ATS/Exchange integrations are standardized through an API derived from the Vertalo GraphQL schema. Because of the high compliance requirements/costs associated with post-issuance trading and transfer, the goal of the Vertalo API is designed to make it as easy as possible to convey data between systems in order to maximize consistency. While the Vertalo platform uses a transaction-based architecture under the hood, we do not currently expose this to the API user and translate trading and transfer calls to transactions as needed. (Future releases may expose low-level transaction calls.)
API calls are ordered, and will be preserved and executed in the order in which they are received. The platform will take instructions typically without regard to the state in which the system may be left. For example, a transfer could result in a securities balance for an investor going below zero. Because of the asynchronous nature of transactions, this state will be allowed (though a warning will be issued).