[3pt14159]

What is important to note is that the ideal use case for Docker is not actually speed - it's about quickly responding to increased load. If you need to vary the number of, say, web servers from 5 to 100 over the day, then Docker is good because you can start them up very quickly.

The down side about docker is that it takes longer to set up your docker in the first place, it is harder to keep secure, and it runs slower than a traditionally deployed application, but compared to VM deployed applications the performance is usually better.