Mongoose/ MongoDB Database Design - node.js

Question

I always have a certain fixed structure in my model (GroupName) and a dynamic part of 1-x (Members).
Group1
GroupName
Member 1
Member 2
Group2
GroupName
Member 1
Group3
GroupName
Member 1
Member 2
Member 3
Is it better to use two tables and connect them later via ids like this:
Groups:
Group1
GroupName
GroupId
Group2
GroupName
GroupId
Members:
Member 1
GroupId
Member 2
GroupId
or to use Schema.Types.Mixed(or anything else)? And how to do it in the second way?
I will always use them in combination later. From a gut feeling I would choose the first method:
http://blog.mongolab.com/2013/04/thinking-about-arrays-in-mongodb/
EDIT:
But even on the second method I have the issue, that one member can belong to multiple groups and I don't want to store him twice. The groups are unique and do only exist once.
But I'm new to MongoDb so I want to learn what's the best option and why.
EDIT II:
I have choosen two divide it into two docs. Is this implementation of the Schemas than correct like this:
var mongoose = require('mongoose');
// define the schema for group model
var groupSchema = mongoose.Schema({
href: {
type: String,
required: true,
unique: true
},
title: String,
members: [id: Schema.Types.ObjectId, name: String]
});
// create the model for users and expose it to our app
module.exports = mongoose.model('group', groupSchema);
&&
var mongoose = require('mongoose');
// define the schema for member model
var memberSchema = mongoose.Schema({
id: {
type:Schema.Types.ObjectId,
required: true,
unique: true
},
amount: String,
name: String
});
// create the model for users and expose it to our app
module.exports = mongoose.model('member', memberSchema);

Answer 1

There is an excellent post on the MongoDB blog which tells us about the various ways a schema can be designed based on the model relationships.
I believe the best schema for you would be to make use of embedded arrays with the member IDs.
//Group
{
_id: '1234',
name: 'some group',
members : [
'abcd',
'efgh'
]
}
EDIT
There is a correction needed in the schema:
// define the schema for group model
var groupSchema = mongoose.Schema({
href: {
type: String,
required: true,
unique: true
},
title: String,
members: [{id: Schema.Types.ObjectId, name: String}] //Needs to be enclosed with braces
});
// create the model for users and expose it to our app
module.exports = mongoose.model('group', groupSchema);

Answer 2

I don't know what your documents contains and if members are a growing array - for example Group1 can have 1-n members in any given moment . if this is the case you should go with option 2: try something like:
{gId: 1, mId: 5}
That is a design best suited for Social graph. Your Group documents will have a fixed size which is good for memory and you can easily get all the members of a group (just don't forget to index gId and mId)
If for each group there is a fixed number of members (or not growing and shrinking to much) then go with option 1
There is a great post by mongoDb team (and also src code) that talks about design.
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