As a Data Infrastructure Engineer you will be responsible for the Data infrastructure of the clients to stay operational. This could involve working in cloud setup as well as on-premise one.
Your day-to-day activity may be split into 3 streams. First, incident management. No one likes incidents but unfortunately their happen. So when they happen you're expected to exclude infrastructural layer from the list of problems or fix the problem. Second, deployment of new components. While we don't think of deployment as hard thing in itself, stitching components together may need a lot of effort. And the third part is actually developing the solutions that we have to make them easier to use.
We are almost 15 years into Big Data era, but the infrastructural part of it is still pre-mature. Commercial solutions are too narrow-scoped while open-source ones are too general and not feature-rich enough. This is why we created a separate infrastructure team that holds the knowledge of deployment and operation of Data components.