FAIR VALUE MEASUREMENTS

Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The following table summarizes our liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):



	December 31, 2017
	Level 1		Level 2		Level 3		Total
Liabilities:
Preferred stock warrants	$	—	$	—	$	2,285	$	2,285
Common stock warrants	—		—		7,945		7,945
Convertible promissory notes	—		—		—		—
Total liabilities	$	—	$	—	$	10,230	$	10,230



	March 31, 2018
	Level 1		Level 2		Level 3		Total
Liabilities:
Preferred stock warrants	$	—	$	—	$	—	$	—
Common stock warrants	—		—		17,666		17,666
Convertible promissory notes	—		—		—		—
Total liabilities	$	—	$	—	$	17,666	$	17,666

Instruments Recorded at Fair Value Using Level 3 Inputs

Our redeemable convertible preferred stock warrants, common stock warrants issued in connection with the Series G Stock financing and our convertible promissory notes are measured and recorded at fair value on a recurring basis using Level 3 inputs. The table below provides a roll forward of the changes in fair value of Level 3 financial instruments (in thousands):



	Preferred Stock Warrants		Common Stock Warrants		Convertible Promissory Notes
Balance at December 31, 2016	$	2,197	$	—	$	72,332
Accrued interest on convertible promissory notes	—		—		1,246
Changes in fair value	327		—		2,606
Balance at March 31, 2017	$	2,524	$	—	$	76,184



	Preferred Stock Warrants			Common Stock Warrants		Convertible Promissory Notes
Balance at December 31, 2017	$	2,285		$	7,945	$	—
Changes in fair value	(549		)	9,721		—
Conversion of preferred stock warrants to common stock warrants	(1,736		)	—		—
Balance at March 31, 2018	$	—		$	17,666	$	—

In valuing our instruments recorded at fair value using Level 3 inputs, our board of directors determined the equity value of our business generally using a combination of the income approach and the market approach valuation methods.

The income approach estimates value based on the expectation of future cash flows that a company will generate, such as cash earnings, cost savings, tax deductions and the proceeds from disposition. These future cash flows are discounted to their present values using a discount rate derived based on an analysis of the cost of capital of comparable publicly traded companies in similar lines of business, as of each valuation date, and is adjusted to reflect the risks inherent in our cash flows.

The market approach estimates the fair value of a company by applying market multiples of comparable publicly traded companies in a similar line of business. The market multiples are based on relevant metrics implied by the price that investors have paid for the equity of publicly traded companies. Given our significant focus on investing in and growing our business, we primarily utilized the forward-looking revenue multiple when performing valuation assessments under the market approach and considered both trading and transaction multiples. When considering which companies to include as our comparable industry peer companies, we focused on U.S.-based publicly traded companies that were broadly comparable to us based on consideration of industry, market and line of business. From the comparable companies, a representative market value multiple was determined and applied to our operating results to estimate the value of our company. The market value multiple was determined based on consideration of multiples of revenue to each of the comparable companies’ historical and forecasted revenue. In addition, the market approach considers IPO and merger and acquisition transactions involving companies similar to the company’s business being valued. Multiples of revenue are calculated for these transactions and then applied to the business being valued, after reduction by an appropriate discount.

Once an equity value was determined, we utilized the option pricing method ("OPM"), or probability-weighted expected return method (“PWERM”) to allocate the overall value of equity to the various share classes. The OPM was used in valuations as of and for dates prior to December 31, 2016 and the PWERM was used in all subsequent valuations. The OPM treats common stock and convertible preferred stock as call options on a company’s enterprise value with exercise prices based on the liquidation preferences of the convertible preferred stock. Under this method, the common stock only has value if the funds available for distribution to stockholders exceed the value of the liquidation preference at the time of an assumed liquidity event. The value assigned to the common stock is the remaining value after the convertible preferred stock is liquidated. The OPM prices the call option using the Black-Scholes model. The PWERM relies on a forward-looking analysis to predict the possible future value of a company. Under this method, discrete future outcomes, including an IPO and non-IPO scenarios, are weighted based on the estimated the probability of each scenario. The PWERM is used when discrete future outcomes can be predicted with reasonable certainty based on a probability distribution. We relied on the PWERM to allocate the value of equity under a liquidity scenario. The projected equity value relied upon in the PWERM scenario was based on (i) guideline IPO transactions involving companies that were considered broadly comparable to us and (ii) our expectation of the pre-money valuation that we needed to achieve to consider an IPO as a viable exit strategy.

The following table summarizes key assumptions used in the PWERM for estimating the fair value of our redeemable convertible preferred stock warrant liability and convertible promissory notes:



	March 31, 2017
Cost of debt applicable to convertible promissory notes	10%
Cost of equity applicable to convertible promissory notes	22%
Weighted-average cost of capital applicable to preferred stock warrants	23%
Discount for lack of marketability	7% to 11%
Volatility	53%
Risk-free interest rate	0.7% to 1.2%

Preferred Stock Warrants

A summary of our preferred stock warrants is as follows (in thousands, except per share amounts):



Preferred Series	Grant date	Expiration date	Exercise price		December 31, 2017	March 31, 2018
Series B-R	2/26/2010	2/25/2020	$	2.36	59	—
Series D-R	9/21/2012	9/20/2022	$	23.64	38	—
Series D-R	9/21/2012	9/20/2022	$	23.64	13	—
Total					110	—

The fair value of the warrants to purchase Series B-R Stock and Series D-R Stock decreased from $26.80 per share and $13.63 per share on December 31, 2017 to $20.18 per share and $10.57 per share on February 8, 2018, respectively, the date at which they converted to warrants to purchase shares of our common stock and were reclassified to additional paid-in capital on our condensed consolidated balance sheet. The decrease in the fair value of the warrants to purchase Series B-R Stock and Series D-R Stock primarily resulted from the timing of future potential liquidity events, changes to our forecasted financial results and changes in the valuation of comparable companies.

Common Stock Warrants Issued in Connection with the Series G Stock Financing

In connection with the Series G Stock financing, we issued warrants to purchase an aggregate number of shares of common stock equal to the product obtained by multiplying 346,334 by a fraction, the numerator of which is the difference between $68.9516 and the volume weighted average closing price of our common stock over the 30 trading days (or such lesser number of days as our common stock has been traded on the Nasdaq Global Market) prior to the date on which such warrants vest and become exercisable and the denominator of which is such volume weighted average closing price, which warrants will become vested and exercisable upon the earlier to occur of the date (i) August, 8, 2018, which is 180 days following the date of our IPO and (ii) 10 days prior to a sale of our company, at an exercise price of $0.0004 per share.

To determine the fair value of our common stock warrant liability issued in connection with our Series G Stock financing, we utilized a Monte Carlo simulation, which allows for the modeling of complex securities and evaluates many possible outcomes to forecast the stock price of the company post-IPO. As part of the valuation, we considered various scenarios related to the pricing, timing and probability of an IPO. We applied an annual equity volatility of 59% and a discount for lack of marketability of 11% to arrive at a valuation of $7.5 million on the issuance date.

Subsequent to our IPO, the fair value of the common stock warrant liability is estimated based on the fair market value of our common stock at each reporting period, discounted from the date of settlement, which is expected to be 180 days following the date of our IPO. The valuation as of March 31, 2018 was determined to be $17.7 million. As a result, during the three months ended March 31, 2018, we recorded a non-cash loss of $9.7 million related to the change in fair value of our common stock warrant liability.

Convertible Promissory Notes

The redemption features included in the terms of the convertible promissory notes were determined to be derivative liabilities due to a significant discount within the redemption features for the note holders. Embedded derivatives that are not clearly and closely related to the host contract are required to be bifurcated and recorded at fair value unless the fair value option is elected on the host contract. Under the fair value option, bifurcation of the embedded derivative is not necessary as all related gains (losses) on the host contract and derivative will be reflected in the consolidated statements of operations. We elected the fair value option for the convertible promissory notes, therefore direct costs and fees associated with the issuance were recognized in earnings as incurred and were not deferred.

To determine the fair value of our convertible promissory notes through their conversion in May 2017, we utilized key assumptions from the PWERM, as shown above. Under this method, we considered the redemption features of the convertible promissory notes to determine the fair value under discrete future outcomes, including IPO and non-IPO scenarios. Under certain non-IPO scenarios, holders of the convertible promissory notes will receive two times preference on the outstanding principal amount. We weighted the fair values based on the estimated probability of each scenario to determine the overall fair value of the convertible promissory notes as of the balance sheet date.

See Note 5—Redeemable Convertible Preferred Stock for a description of the Series G Stock financing in May 2017 that resulted in the conversion of the convertible promissory notes into shares of our Series G’ Stock.

Performance-based Warrants Issued to FIS

In May 2013, we granted 10-year performance-based warrants to purchase up to 644,365 shares of Series E Stock at an exercise price of $23.64 per share. Since FIS did not participate in the convertible promissory note financing, their warrants to purchase preferred stock were converted to warrants to purchase common stock. The warrants vested upon the completion of our IPO in February 2018 resulting in a non-cash expense of $2.5 million. We determined the fair value of these common warrants on the date of IPO using the Black-Scholes option pricing model, which is affected by the fair value of our common stock as well as the following significant inputs:



	Performance-based warrants (vested upon IPO)
Weighted-average grant date fair value	$3.91
Significant inputs:
Value of common stock	$13.00
Expected term	5.3 years
Volatility	50%
Risk-free interest rate	2.0%
Dividend yield	—%