I was too, of course a distributed system could also be built with DCOM and MTC (later COM+), and the DTC (Distributed Transaction Coordinator) could be used wh

I was too, of course a distributed system could also be built with DCOM and MTC (later COM+), and the DTC (Distributed Transaction Coordinator) could be used when you needed a transaction across services (or DBs, or MQs). Obviously the DTC was developed in recognition of the fact that distributed transactional service calls were a real requirement - something that current microservice architectures over HTTP REST don't seem to support.