What is the best way to make user "variables" in MongoDB?

Question

MongoDB

Actually, with the transition to mongu, the question arose - how best (for the speed of obtaining this data in the future, etc.) to store user variables?
Let's say the user Vasya wanted to create variables name = Vasya, yold = 21, car = Lada Kalina. In muscle, I would store this as:
user_id | var_key | var_value
2 | name | Vasya
2 | old | 21
2 | car | Lada Kalina
Later, I can easily pull out the values ​​of the variables with the query SELECT var_value FROM variables WHERE user_id=2 AND var_key='name' ...
With mongo, I found 2 ways to store such variables.
Method 1:

{
    user_id: 2,
    variables:  [
        {
            var_key: 'name',
            var_value: 'Вася'
        },
        {
            var_key: 'yold',
            var_value: 21
        }
        ...
    ]
}

Method 2:

{
    user_id: 2,
    variables:  {
        name: 'Вася',
        yold: 21,
        ...
    }
}

Which option would be more convenient to use? Or maybe there are some other options?

Answer 1

1) You can add duplicate keys, you can index all values ​​​​with one index (because the key name is one), this list can be done by add / del
2) It is easier to update the value (in a direct way), gives uniqueness by key - there will be no duplicate keys by element.
Each approach has its own merits.
You can also do it the same way as in mysql, but this is often inefficient.