a dev can build a thing, an engineer can build a distributed modular thing with more complexity around non programming parts like infrastructure. Take the thing and design a machine of parts and each can be maintained, observed, and optimized as needed. For example we can use topics for backpressure and consumer lag for auto scaling pods, but then you have to consider the distributed processing for duplication, out of order, throughput… there is no exact line in the sand between dev and engineer but that’s how I think of it.