Common Stock and Stockholders' Equity (Deficit) (Tables)
 3 Months Ended
Apr. 30, 2019
Equity [Abstract]  
Schedule of Stock Option Activity
Stock option activity is as follows:
 
Number of
Shares
 
Weighted
Average Exercise
Price
 
Weighted
Average
Remaining
Contractual Term
 
Aggregate
Intrinsic Value
 
 
 
 
 
 
 
(in thousands)
Balance at January 31, 2019
14,006,222

 
$
4.32

 
8.2 years
 
$
142,840

Granted
3,682,821

 
$
15.04

 
 
 
 
Exercised
(951,830
)
 
$
2.37

 
 
 
 
Forfeited
(208,525
)
 
$
6.13

 
 
 
 
Balance at April 30, 2019
16,528,688

 
$
6.80

 
8.4 years
 
$
662,726

Vested as of April 30, 2019
5,743,831

 
$
2.74

 
7.4 years
 
$
253,662
Schedule of Assumption Used to Calculate the Fair Value of Employee Stock Option Grants
The following assumptions were used to calculate the fair value of employee stock option grants made during the periods:
 
Three Months Ended April 30,
 
2019
 
2018
Expected dividend yield
—
%
 
—
%
Expected volatility
42.4% - 42.8%

 
40.9% - 41.0%

Expected term (years)
5.5 - 6.9

 
5.8 - 6.1

Risk-free interest rate
2.32% - 2.48%

 
2.60% - 2.72%
Schedule of Stock-based Compensation Expense
Stock-based compensation expense included in the Company’s condensed consolidated statements of operations is as follows (in thousands):
 
Three Months Ended April 30,
 
2019
 
2018
Cost of revenue
$
143

 
$
61

Research and development
860

 
715

Sales and marketing
1,464

 
852

General and administrative
2,345

 
1,529

Total
$
4,812

 
$
3,157