When is a good time to get started?

When my daughter was 4.5 years old she started piano playing based on a specific early children education. Now 3 years later she is doing really well and still enjoys it a lot. It sounds early, but if the education is done right I believe there is nothing wrong exposing them early on.

For learning how to code (a little) I am not sure when it is a good starting point. It seems to me at 4th grade they have enough comprehension to learn some basic coding skills. For a parent finding the right balance for the child of having fun, learning and accomplishing something is probably the crucial part.