[rezonant]

Considering the vast majority of exploits are at the application level (SQLi, XSS, etc), putting barriers between your various applications is a good thing to do. Sure, you could run 10 apps on 10+ VMs, but it's not cost efficient, and then you just have more servers to manage. If the choice is between run 10 "bare metal" apps on 1 VM or run 10 containers on 1 VM, I'll pick containers every time.

At that point, why are we making a distinction when we do run 1 app on one VM? Sure, containers have some overhead, but not enough for it to be a major concern for most apps, especially if you need more than 1 VM for the app anyway (horizontal scaling). The major attack vector added by containers is the possibility of container breakout, which is very real. But if you run that 1 app outside the container on that host, they don't have to break out of the container when they get RCE.

[supriyo-biswas]

The VM/container distinction is less relevant to this discussion than you might think; both Amazon ECS and fly.io run customer workloads in VMs (“microVMs” in their lingo).