Comment by fluorinerocket

In MDAO you definitely know all the constraints at compile time, but inequality constraints can be active or inactive as the optimizer progresses.

That's how SNOPT, IPOPT, presumably KNITRO and nonlinear programming optimizers work.

Yes MDAO is "just" constrained nonlinear optimization.

You come up with a model for your thing, which often involves multiple "disciplines" like mass, propulsion, aerodynamics, loads, trajectory/equations of motion, and then usually use some framework to calculate the constraints values and objective value and their gradients