Exhibit 24.2

POWER OF ATTORNEY

Know all by these presents, that the undersigned hereby authorizes James T. Beck, for so long as he is an employee, member or partner of Mayfield, to execute for and on behalf of the undersigned, in the undersigned’s individual capacity, in the undersigned’s capacity as a member of any limited liability company and in the undersigned’s capacity as a partner of any general or limited partnership, (i) any and all filings pursuant to Section 16 of the Securities Exchange Act of 1934 (the “Exchange Act”), including any and all Forms 3, 4 and 5, and Section 13 of the Exchange Act, including Schedules 13D and 13G, and any amendments thereto and joint filing agreements and other documents in connection therewith, and (ii) any applications for EDGAR access codes, including the Form ID, in each case as may be required to be filed from time to time with the U. S. Securities and Exchange Commission with respect to any investments of Mayfield Fund and its affiliates (collectively, “Mayfield”), and cause any and all of such forms, schedules, agreements and documents to be filed with the U. S. Securities and Exchange Commission pursuant to Section 13 and Section 16 of the Exchange Act, relating to the undersigned’s direct or indirect beneficial ownership of securities (in the undersigned’s individual capacity, or in the undersigned’s capacity as a member of any limited liability company or partner in any general or limited partnership). The undersigned hereby grants to such attorney-in-fact full power and authority to do and perform any and every act and thing whatsoever requisite, necessary or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact, or such attorney-in-fact substitute or substitutes, shall

lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted. The undersigned acknowledges that the foregoing attorney-in-fact, in serving in such capacity at the request of the undersigned, is not assuming, nor is Mayfield assuming, any of the undersigned’s responsibilities to comply with Section 16 or Section 13 of the Exchange Act.

This Power of Attorney shall remain in full force and effect until the undersigned is no longer an employee, member or partner of Mayfield, unless earlier revoked by the undersigned in a signed writing delivered to the foregoing attorney-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of this 31st day of January, 2011.

    /s/ Robert T. Vasan

Name: Robert T. Vasan