DevOps (a clipped compound of "development" and "operations") is a software engineering culture and practice that aims at unifying software development (Dev) and software operation (Ops)
Giving developers operational responsibilities has greatly enhanced the quality of the services , both from a customer and a technology point of view. The traditional model is that you take your software to the wall that separates development and operations, and throw it over and then forget about it. Not at Amazon. You build it, you run it. This brings developers into contact with the day-to-day operation of their software. It also brings them into day-to-day contact with the customer. This customer feedback loop is essential for improving the quality of the service.
- A conversation with Werner Vogels - 30/Jun/2006https://queue.acm.org/detail.cfm?id=1142065
You build it, you run it is the principle that development teams operate their own product.
Monitoring based on metrics exposed by the internals of the system, including logs, interfaces like the Java Virtual Machine Profiling Interface, or an HTTP handler that emits internal statistics.
Testing externally visible behavior as a user would see it.
Working software in production