mongoose.Schema({
    user_id: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'users',
        required: true,
    },
    coin_code: { type: String, required: true, },
    coin_balance: { type: Number, default: 0 },
    status: { type: Boolean },
    created_date: { type: Date },
    modified_date: { type: Date },
});

let updated_coin_merchant = await coin_merchant_model.findOneAndUpdate(
    {
        user_id: user_id,
        coin_code: coin_code
    }, {
        $inc: { coin_balance: Number(new_amount) }
    }, { new: true }
);