In a short post on IH? You do have high expectations of me. For the sheer joy of it, I will offer you this...
Democracy is sometimes simplified to:
Rule of the people,
Rule by the people,
Rule for the people
Let's say 'the people' is a set containing all individuals in our society.
The definition would become (the aggregate of):
Rule of the individual
By the individual
For the individual
Each individual can decide to pursue their rational self-interest, to not allow themselves to be sacrificed for the sake of others, and to not force others to be sacrificed for their own sake.
Choosing to act in accordance with those three conditions would prevent an individual from carrying out rule of themselves, by themselves, for themselves in a way that violates the individual rights of any other individual. The choice an individual makes in this respect, will determine if they are just or not.
A written constitution consistent with Objectivism would be used by the Government (i.e. the individuals that form it) to ensure justice is maintained; so disputes can be resolved and individuals whose conduct is unjust can be dealt with appropriately. The function of the Government would include an effective police force, prison service and an effective military as complimentary priorities.
There would still be elections, to ensure the political group the population judges to be most competent, is permitted to carry out these functions.
This kind of democracy would be very different from what we are familiar with, but it would be both functioning and 'non-collective' as you put it.