Lafcadio will support transactions as long as the underlying table type will support them. This is done using blocks; when the block is exited, the transaction is committed. For example, in a PayPal-like system where you're transferring money from one user to another, you want transactions to make sure all the rows are recorded or none of them are.

object_store = Lafcadio::ObjectStore.get_object_store
object_store.transaction do |tr|
  from_account.update!( 'amount' => from_account.amount - transfer_amount )
  to_account.update!( 'amount' => to_account.amount + transfer_amount )
end

Rollbacks work by calling the rollback method on the transactional object passed through the block.

object_store.transaction do |tr|
  from_account.update!( 'amount' => from_account.amount - transfer_amount )
  tr.rollback
  to_account.update!( 'amount' => to_account.amount + transfer_amount )
end

In fact, raising any sort of error within the transaction will rollback the transaction.

object_store.transaction do |tr|
  from_account.update!( 'amount' => from_account.amount - transfer_amount )
  raise "just kidding"
  to_account.update!( 'amount' => to_account.amount + transfer_amount )
end

Note also that the MockObjectStore handles transactions as well. This means that you can write unit-tests testing transaction-dependent logic, and test them in-memory.