SEC Form 3 
FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940 	  
OMB APPROVAL
OMB Number:	3235-0104	
Estimated average burden	
hours per response:	0.5	

	
1. Name and Address of Reporting Person*
McCarthy Shaun N.	

(Last)	(First)	(Middle)	
C/O CASA SYSTEMS, INC.	
100 OLD RIVER ROAD	

(Street) 
ANDOVER	MA	01810	

(City)	(State)	(Zip)	
	2. Date of Event Requiring Statement (Month/Day/Year)
08/15/2018 	3. Issuer Name and Ticker or Trading Symbol 
Casa Systems Inc [ CASA ] 		
		4. Relationship of Reporting Person(s) to Issuer 
(Check all applicable) 
	Director		10% Owner	
X	Officer (give title below)		Other (specify below)	
Interim CFO	
	5. If Amendment, Date of Original Filed (Month/Day/Year)				
			6. Individual or Joint/Group Filing (Check Applicable Line) 
X	Form filed by One Reporting Person	
	Form filed by More than One Reporting Person	
	
Table I - Non-Derivative Securities Beneficially Owned	
1. Title of Security (Instr. 4) 	2. Amount of Securities Beneficially Owned (Instr. 4) 	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 	4. Nature of Indirect Beneficial Ownership (Instr. 5) 	
Table II - Derivative Securities Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities) 	
1. Title of Derivative Security (Instr. 4) 	2. Date Exercisable and Expiration Date (Month/Day/Year)	3. Title and Amount of Securities Underlying Derivative Security (Instr. 4) 	4. Conversion or Exercise Price of Derivative Security 	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 	6. Nature of Indirect Beneficial Ownership (Instr. 5) 	
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares				
Stock option (right to buy)	(1) 	06/10/2024	Common Stock	31,925	2.29	D		
Restricted Stock Units(2) 	(3) 	(3) 	Common Stock	5,405	0.00	D		
Explanation of Responses:	
1. The option is currently vested as to 30,360 shares, and the remaining 1,565 shares are scheduled to vest on August 31, 2018.	
2. Each Restricted Stock Unit ("RSU") represents the right to receive one share of common stock, $0.001 par value per share (the "Common Stock") of Casa Systems, Inc. (the "Company") upon vesting, subject to the reporting person's continued service relationship with the Company and the other terms and conditions set forth in the applicable RSU agreement. In the sole discretion of the Company's board of directors, the Company may, with respect to any applicable vesting date, deliver to the reporting person Common Stock or cash having a fair market value equal to the number of shares of Common Stock underlying the portion of the RSU that vested on such date, payable within 30 days of the vesting date, less applicable taxes.	
3. The RSUs are scheduled to vest as to 25% of the original number of RSUs on June 14, 2019, and as to an additional 25% upon completion of each year thereafter.	
Remarks:	
Exhibit 24.1 - Limited Power of Attorney for Section 16 Reporting Obligations	
	/s/ Todd Keebaugh, attorney-in-fact	08/22/2018	
	** Signature of Reporting Person	Date	
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.	
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).	
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).	
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.	
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.	

LIMITED POWER OF ATTORNEY FOR SECTION 16 REPORTING OBLIGATIONS

       Know all by these present, that the undersigned hereby makes, constitutes
and appoints each of Jerry Guo and Todd Keebaugh, signing singly and
each acting individually, as the undersigned's true and lawful attorney-in-fact
with full power and authority as hereinafter described to:

        (1) execute for and on behalf of the undersigned, in the undersigned's
capacity as a director, officer and/or stockholder of Casa Systems, Inc. (the
"Company"), Forms 3, 4, and 5 (including any amendments thereto) in accordance
with Section 16(a) of the Securities Exchange Act of 1934 and the rules
thereunder (the "Exchange Act");

        (2) do and perform any and all acts for and on behalf of the undersigned
which may be necessary or desirable to prepare, complete and execute any such
Form 3, 4, or 5, prepare, complete and execute any amendment or amendments
thereto, and timely deliver and file such form with the United States Securities
and Exchange Commission (the "SEC") and any stock exchange or similar authority,
including without limitation the filing of a Form ID or any other application
materials to enable the undersigned to gain or maintain access to the Electronic
Data Gathering, Analysis and Retrieval system of the SEC;

        (3) seek or obtain, as the undersigned's representative and on the
undersigned's behalf, information regarding transactions in the Company's
securities from any third party, including brokers, employee benefit plan
administrators and trustees, and the undersigned hereby authorizes any such
third-party to release any such information to the herein appointed attorney in
fact and approves and ratifies any such release of information; and

        (4) take any other action of any type whatsoever in connection with the
foregoing which, in the opinion of such attorney-in-fact, may be of benefit
to, in the best interest of, or legally required by, the undersigned, it being
understood that the documents executed by such 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 such attorney in fact may approve in
such 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, in serving in such capacity at the request of the
undersigned, are not assuming nor relieving, nor is the Company assuming nor
relieving, any of the undersigned's responsibilities to comply with Section 16
of the Exchange Act.  The undersigned acknowledges that neither the Company nor
the foregoing attorneys-in-fact assume (i) any liability for the undersigned's
responsibility to comply with the requirement of the Exchange Act, (ii) any
liability of the undersigned for any failure to comply with such requirements,
or (iii) any obligation or liability of the undersigned for profit disgorgement
under Section 16(b) of the Exchange Act.

      This Power of Attorney shall remain in full force and effect until 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,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys in fact.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 22nd day of August, 2018.

/s/ Shaun N. McCarthy
Shaun N. McCarthy