Sec Form 3 Filing - OpenView Management, LLC @ Datadog, Inc. - 2019-09-18

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person OpenView Management, LLC 2. Issuer Name and Ticker or Trading Symbol Datadog, Inc. [ DDOG] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 303 CONGRESS STREET, 7TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 09/18/2019 (Street) BOSTON, MA02210 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series B Preferred Stock ( 1 ) ( 1 ) ( 1 ) FN ( 1 ) ( 2 ) 25,115,388 D ( 3 ) Series C Preferred Stock ( 1 ) ( 1 ) ( 1 ) FN ( 1 ) ( 2 ) 10,070,100 D ( 3 ) Series D Preferred Stock ( 1 ) ( 1 ) ( 1 ) FN ( 1 ) ( 2 ) 5,622,792 D ( 3 ) Series B Preferred Stock ( 1 ) ( 1 ) ( 1 ) FN ( 1 ) ( 2 ) 981,396 D ( 4 ) Series C Preferred Stock ( 1 ) ( 1 ) ( 1 ) FN ( 1 ) ( 2 ) 393,492 D ( 4 ) Series D Preferred Stock ( 1 ) ( 1 ) ( 1 ) FN ( 1 ) ( 2 ) 219,708 D ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other OpenView Management, LLC 303 CONGRESS STREET, 7TH FLOOR BOSTON, MA02210 X OpenView General Partner III, L.P. 303 CONGRESS STREET, 7TH FLOOR BOSTON, MA02210 X OpenView Affiliates Fund III, L.P. 303 CONGRESS STREET, 7TH FLOOR BOSTON, MA02210 X OpenView Venture Partners III, L.P. 303 CONGRESS STREET, 7TH FLOOR BOSTON, MA02210 X Signatures /s/ Rufus King, Chief Legal Officer of OpenView Management, LLC 09/18/2019 Signature of Reporting Person Date /s/ Rufus King, Chief Legal Officer of OpenView Management, LLC, the general partner of OpenView General Partner III, L.P. 09/18/2019 Signature of Reporting Person Date /s/ Rufus King, Chief Legal Officer of OpenView Management, LLC, the general partner of OpenView General Partner III, L.P., the general partner of OpenView Affiliates Fund III, L.P. 09/18/2019 Signature of Reporting Person Date /s/ Rufus King, Chief Legal Officer of OpenView Management, LLC, the general partner of OpenView General Partner III, L.P., the general partner of OpenView Venture Partners III, L.P. 09/18/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Preferred Stock is convertible into Class B Common Stock on a 1:1 basis and has no expiration date. Immediately prior to the closing of the Issuer's initial public offering, (1) all shares of Preferred Stock will be automatically converted into shares of Common Stock on a 1:1 basis and (2) all shares of Common Stock shall then be reclassified into one share of Class B Common Stock on a 1:1 basis. ( 2 )After the completion of the Issuer's initial public offering, on any transfer of shares of Class B common stock, whether or not for value, each such transferred share will automatically convert into one share of Class A common stock, except for certain transfers described in the Issuer's amended and restated certificate of incorporation, including transfers for tax and estate planning purposes, so long as the transferring holder continues to hold sole voting and dispositive power with respect to the shares transferred. Additionally, the shares of Class B common stock will convert automatically into Class A common stock, on a 1:1 basis, upon the tenth anniversary of the Issuer's initial public offering. ( 3 )The securities are held by OpenView Venture Partners III, L.P. ("OVP III LP"). OpenView Management, LLC ("OVM LLC") is the general partner of OpenView General Partner III, L.P. ("OGP III LP"), which is the general partner of OVP III LP. Each of OVM LLC and OGP III LP disclaims beneficial ownership of all the shares held by OVP III LP except to the extent, if any, of its pecuniary interest therein and this report shall not be deemed an admission that it is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose. ( 4 )The securities are held by OpenView Affiliates Fund III, L.P. ("OAF III LP"). OGP III LP is the general partner of OAF III LP. Each of OVM LLC and OGP III LP disclaims beneficial ownership of all the shares held by OAF III LP except to the extent, if any, of its pecuniary interest therein and this report shall not be deemed an admission that it is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

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