POWER OF ATTORNEY

(For Executing Form ID and Forms 3, 4 and 5)

Know all by these presents, that the undersigned hereby constitutes and
appoints each of Andrew Stephens and Sophie Hubscher of MongoDB, Inc. (the "Company")
and Nicole Brookshire and Alison Haggerty of Cooley LLP with full power of
substitution, signing individually, the undersigned's true and lawful attorneys
-in fact and agents to:

(1) Prepare, execute in the undersigned's name and on the
undersigned's behalf, and submit to the Securities and Exchange Commission (the
"SEC") Form ID and Forms 3, 4 and 5 (including amendments thereto and joint
filing agreements in connection therewith) in accordance with Section 16(a) of
the Securities Exchange Act of 1934, as amended (the "Exchange Act") and the
rules thereunder in the undersigned's capacity as an officer, director or
beneficial owner of more than 10% of a registered class of securities of the
Company;

(2) Do and perform any and all acts for and on behalf of the
undersigned that may be necessary or desirable to prepare and execute any such
Form ID and Forms 3, 4 or 5 (including amendments thereto and joint filing
agreements in connection therewith) and timely file such forms with the SEC and
any stock exchange, self-regulatory association or any similar authority; and

(3) Take any other action of any type whatsoever in connection with
the foregoing that, in the opinion of such attorney-in-fact, may be of benefit
to, in the best interest of, or legally required of the undersigned, it being
understood that the documents executed by the attorney-in-fact on behalf of the
undersigned pursuant to this Power of Attorney shall be in such form and shall
contain such terms and conditions as the attorney-in-fact may approve in the
attorney-in-fact's discretion.

The undersigned hereby grants to each 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's 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 attorneys-in-fact, and their substitutes, in serving in such capacity
at the request of the undersigned, are not assuming (nor is the Company
assuming) any of the undersigned's responsibilities to comply with Section 16
of the Exchange Act.

This Power of Attorney shall remain in full force and effect until the
earliest to occur of (a) the undersigned is no longer required to file Forms 3,
4 and 5 with respect to the undersigned's holdings of and transactions in
securities issued by the Company, (b) revocation by the undersigned in a signed
writing delivered to the Company and the foregoing attorneys-in fact or (c) as
to any attorney-in-fact individually, until such attorney-in-fact is no longer
employed by the Company, or any of its subsidiaries, or Cooley LLP, as
applicable.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney
to be executed as of the date written below.

Date: January 20, 2020

By: /s/Mark Porter
Mark Porter