cordapp-template-kotlin | Kotlin CorDapp Template | Application Framework library

Corda Opensource doesn't have a multi-threaded flow state machine. Hence you won't be able to benefit from parallel flow execution on Corda Opensource.

A better approach for this with Corda Opensource would perhaps be batching of accounts with a single transaction on flow, rather than creating the accounts with multiple flow invocation.

With Corda Enterprise, however, you could benefit with multi-threaded flow state machine. But I would still recommend exploring the batching approach and find an optimal solution with maximum efficiency.

Two reasons for this:

1. Each Corda transaction also includes the jar containing the contract definition as an attachment. This is done to ensure that the correct contract is available when a transaction is validated at a later point in time (Considering the contract may upgrade over time). Thus separating the contract and flows jar reduces the size of the contract jar being attached to the transaction and thus reduces the size of the transaction. See more here: https://docs.corda.net/writing-a-cordapp.html#modules

2. It helps in upgrades. Contracts have constraints and thus contract upgrades take a rather complex path. Also, we anticipate that the contacts are less prone to upgrades than the flows. Hence separating them in separate modules allows for easy upgrades when one just requires to upgrade the flows, which can be done just by replacing the old flow jar with the newer one. Learn more here: https://medium.com/corda/contract-upgrades-and-constraints-in-corda-425055a9a47f