Indeed, James Turnbull, then Docker's VP of services and support, told me at the conference that three of its largest beta bank customers were moving it into production. That's a heck of a confident move for any 1.0 technology, but it's almost unheard of in the safety-first financial world.

Today, Docker, and its open-source father now named Moby, is bigger than ever. According to Docker, over 3.5 million applications have been placed in containers using Docker technology and over 37 billion containerized applications have been downloaded.

It's not just Docker who thinks they're on to something big. 451 Research also sees Docker technology being wildly successful. It predicts "the application container market will explode over the next five years. Annual revenue is expected to increase by 4x, growing from $749 million in 2016 to more than $3.4 billion by 2021, representing a compound annual growth rate (CAGR) of 35 percent."

Real-world data backs up the conclusion that Docker is being widely adopted. DataDog, a cloud-monitoring system, found that by March 2016, "13.6 percent of Datadog's customers had adopted Docker. One year later that number has grown to 18.8 percent. That's almost 40 percent market-share growth in 12 months." RightScale observed in its RightScale 2018 State of the Cloud report that Docker's adoption by the industry has increased to 49 percent from 35 percent in 2017.

Docker, an open-source technology, isn't just the darling of Linux powers such as Red Hat and Canonical. Proprietary software companies such as Oracle and Microsoft have also embraced Docker. Today, almost all IT and cloud companies have adopted Docker.