Sec Form 4 Filing - Le-Quoc Alexis @ Datadog, Inc. - 2019-09-23

FORM 4 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 Le-Quoc Alexis 2. Issuer Name and Ticker or Trading Symbol Datadog, Inc. [ DDOG] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) President & CTO (Last) (First) (Middle) C/O DATADOG, INC., 620 8TH AVENUE, 45TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 09/23/2019 (Street) NEW YORK, NY10018 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 Common Stock 09/23/2019 J 13,558,395 ( 1 ) D 0 I See footnote ( 2 ) Common Stock 09/23/2019 J 3,505,569 ( 1 ) D 0 I See footnote ( 3 ) Common Stock 09/23/2019 J 600,000 ( 1 ) D 0 I See footnote ( 4 ) Common Stock 09/23/2019 J 600,000 ( 1 ) D 0 I See footnote ( 5 ) Common Stock 09/23/2019 J 600,000 ( 1 ) D 0 I See footnote ( 6 )

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 Class B Common Stock ( 7 ) 09/23/2019 J 13,558,395 ( 7 ) ( 7 ) Class A Common Stock 13,558,395 $ 0 13,558,395 I See footnote ( 2 ) Class B Common Stock ( 7 ) 09/23/2019 J 3,505,569 ( 7 ) ( 7 ) Class A Common Stock 3,505,569 $ 0 3,505,569 I See footnote ( 3 ) Class B Common Stock ( 7 ) 09/23/2019 J 600,000 ( 7 ) ( 7 ) Class A Common Stock 600,000 $ 0 600,000 I See footnote ( 4 ) Class B Common Stock ( 7 ) 09/23/2019 J 600,000 ( 7 ) ( 7 ) Class A Common Stock 600,000 $ 0 600,000 I See footnote ( 5 ) Class B Common Stock ( 7 ) 09/23/2019 J 600,000 ( 7 ) ( 7 ) Class A Common Stock 600,000 $ 0 600,000 I See footnote ( 6 ) Stock Option (Right to Buy) $ 0.3067 09/23/2019 J 4,507,200 ( 8 ) 10/27/2025 Common Stock ( 1 ) 4,507,200 $ 0 0 D Stock Option (Right to Buy) $ 0.3067 09/23/2019 J 4,507,200 ( 8 ) 10/27/2025 Class B Common Stock ( 7 ) 4,507,200 $ 0 4,507,200 D Stock Option (Right to Buy) $ 0.9092 09/23/2019 J 1,296,000 ( 9 ) 10/25/2027 Common Stock ( 1 ) 1,296,000 $ 0 0 D Stock Option (Right to Buy) $ 0.9092 09/23/2019 J 1,296,000 ( 9 ) 10/25/2027 Class B Common Stock ( 7 ) 1,296,000 $ 0 1,296,000 D Stock Option (Right to Buy) $ 10.74 09/23/2019 J 900,000 ( 10 ) 07/19/2029 Common Stock ( 1 ) 900,000 $ 0 0 D Stock Option (Right to Buy) $ 10.74 09/23/2019 J 900,000 ( 10 ) 07/19/2029 Class B Common Stock ( 7 ) 900,000 $ 0 900,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Le-Quoc Alexis C/O DATADOG, INC. 620 8TH AVENUE, 45TH FLOOR NEW YORK, NY10018 X President & CTO Signatures Alexis Le-Quoc, by /s/ Ron A. Metzger, Attorney-in-Fact 09/23/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Immediately prior to the closing of the Issuer's initial public offering, each share of Common Stock was reclassified into one share of Class B Common Stock in an exempt transaction pursuant to Rule 16b-7. ( 2 )Shares are held directly by the Alexis Le-Quoc Revocable Trust. ( 3 )Shares are held directly by the Alexis Le-Quoc 2016 GRAT. ( 4 )Shares are held directly by the Pomel Descendents' 2018 Trust, of which the Reporting Person is Trustee. ( 5 )Shares are held directly by the Artemis Le-Quoc 2018 Trust. ( 6 )Shares are held directly by the Agathe Le-Quoc 2018 Trust. ( 7 )Each share of Class B Common Stock is convertible at any time at the option of the Reporting Person into one share of Class A Common Stock and has no expiration date. Each share of Class B Common Stock will convert automatically into one share of Class A Common Stock upon the earliest of: (i) any transfer, whether or not for value, except for certain "Permitted Transfers" as defined in the Issuer's amended and restated certificate of incorporation, (ii) the nine-month anniversary of the death of the Reporting Person in the case of shares held directly or in a trustee capacity, and (iii) the tenth anniversary of the Issuer's initial public offering of its Class A Common Stock. ( 8 )Fully vested and exercisable. ( 9 )Option vests as to 25% on March 1, 2018 and in equal monthly installments thereafter over three years. ( 10 )1/36th of Reporting Person's options vest on the earlier of January 1, 2021 and the one-year anniversary of the Issuer's initial public offering(such date, the "Initial Vesting Date"). Thereafter, 1/36th of the options vest monthly on the same day in each month as the Initial Vesting Date.In addition, the grant agreement provides for an "early exercise" feature subject to the Issuer's right to repurchase unvested shares upon theReporting Person's termination from the Issuer's board of directors.

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