Insert with join

In a simple test scenario, I have a Performer and a PerformerType model.
My models are the following, for the Performer:

export interface IPerformer {
    name: string;
    pictures: Array<string>;
    performerType: Types.ObjectId

export interface IPerformerSaveRequest{
    name: string;
    pictures: Array<string>;
    performerTypeKey: number

const PerformerSchema: Schema = new Schema({
    name: { type: String, required: true },
    pictures: { type: Array<String>, required: false },
    performerType: { type: Types.ObjectId, ref: 'PerformerType' }

And for the PerformerType:

export interface IPerformerType {
    key: number;
    value: string;

const PerformerTypeSchema: Schema = new Schema({
    key: { type: Number, required: true, unique: true},
    value: { type: String, required: true }

When I insert a new performer I would like to reference the type through a key rather that its objectId, that’s why I made IPerformerSaveRequest with a key.
I would like to understand the most correct and performant way to do this in MongoDB with mongoose (Express js with typescript, not that it matters), in SQL I would make a classic insert with a join statement to get the Id from the PerformerType table, what’s the equivalent here?
I want to emphasize that I would really like to understand the correct way to do it, not just a way, I know I could retrieve the values and assign them with some map function, but I guess it’s not the right way to do it.