Computer implemented method, system and computer usable program code for achieving transactional quality of service in a transactional object store system. A transaction is received from a client and is executed, wherein the transaction comprises reading a read-only derived object, or reading or writing another object, and ends with a decision to request committing the transaction or a decision to request aborting the transaction. Responsive to a decision to request committing the transaction, wherein the transaction comprises writing a publishing object, events are delivered to event stream processing queries, and are executed in parallel with executing of the transaction. Responsive to a decision to request committing a transaction that comprises reading a read-only derived object, a validation is performed to determine whether the transaction can proceed to be committed, whether the transaction should abort, or whether the validation should delay waiting for one or more event stream processing queries to complete.