ATEN A10 Networks Inc

The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

  Names of Reporting Persons

  Summit Partners, L.P.

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  PN    

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Partners GE VIII, LLC

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  OO

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Partners GE VIII, L.P.

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  PN    

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Partners Growth Equity Fund VIII-A, L.P.

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  PN    

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Partners Growth Equity Fund VIII-B, L.P.

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  PN    

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Master Company, LLC

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  OO

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Investors Management, LLC

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  OO

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Investors I, LLC

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Delaware

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  OO

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Summit Investors I (UK), L.P.

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  Cayman Islands

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  PN    

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Martin J. Mannion

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  United States of America

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  IN    

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

  Names of Reporting Persons

  Peter Y. Chung

  Check The Appropriate Box if a Member of a Group (See Instructions)

  (a)  ☐        (b)  ☐

  SEC Use Only

  Citizenship or Place of Organization

  United States of America

Number of

Shares

 Beneficially 

Owned By

Each

Reporting

Person

With

  Sole Voting Power

  0

  Shared Voting Power

  3,877,890

  Sole Dispositive Power

  0

  Shared Dispositive Power

  3,877,890

  Aggregate Amount Beneficially Owned by Each Reporting Person

  3,877,890

  Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares

  ☐

  Percent of Class Represented By Amount in Row (9)

  5.28%⁽¹⁾

  Type of Reporting Person (See Instructions)

  IN    

Calculated based on 73,447,815 shares of common stock, par value $0.00001 per share outstanding as of October 28, 2022 as reported on the Issuer’s Form 10-Q, filed on November 3, 2022.

2300 Orchard Parkway

San Jose, California 95131

This Schedule 13G is being filed by Summit Partners, L.P., Summit Partners GE VIII, LLC, Summit Partners GE VIII, L.P., Summit Partners Growth Equity Fund VIII-A, L.P., Summit Partners Growth Equity Fund VIII-B, L.P., Summit Master Company, LLC, Summit Investors Management, LLC, Summit Investors I, LLC, Summit Investors I (UK), L.P. (individually, an “Entity” and collectively, the “Entities”), Martin J. Mannion and Peter Y. Chung (each of the foregoing Entities or individuals, a “Reporting Person”).

Summit Master Company, LLC is the (i) general partner of Summit Partners, L.P., which is the managing member of Summit Partners GE VIII, LLC, which is the general partner of Summit Partners GE VIII, L.P., which is the general partner of Summit Partners Growth Equity Fund VIII-A, L.P. and Summit Partners Growth Equity Fund VIII-B, L.P. and (ii) managing member of Summit Investors Management, LLC, which is the manager of Summit Investors I, LLC and the general partner of Summit Investors I (UK), L.P. Summit Master Company, LLC, as general partner of Summit Partners, L.P. and the managing member of Summit Investors Management, LLC, has delegated investment decisions, including voting and dispositive power, to Summit Partners, L.P. and its investment committee responsible for voting and investment decisions with respect to A10 Networks, Inc. Summit Partners, L.P., through a two-person investment committee responsible for voting and investment decisions with respect to A10 Networks, Inc., currently composed of Martin J. Mannion and Peter Y. Chung, has voting and dispositive authority over the shares held by the reporting persons, as applicable.

Ownership

(a)   Amount beneficially owned:

See responses to Item 9 on each cover page.

(b)  Percent of Class:

See responses to Item 11 on each cover page.

(c)   Number of shares as to which the Reporting Person has:

(i) Sole power to vote or to direct the vote:

See responses to Item 5 on each cover page.

(ii)  Shared power to vote or to direct the vote:

See responses to Item 6 on each cover page.

(iii)  Sole power to dispose or to direct the disposition of:

See responses to Item 7 on each cover page.

(iv) Shared power to dispose or to direct the disposition of:

See responses to Item 8 on each cover page.

Of the 3,877,890 reported securities, (i) Summit Partners Growth Equity Fund VIII-A, L.P. directly holds 2,717,692 shares of Common Stock, (ii) Summit Partners Growth Equity Fund VIII-B, L.P. directly holds 992,866 shares of Common Stock, (iii) Summit Investors I, LLC directly holds 15,889 shares of Common Stock, (iv) Summit Investors I (UK), L.P. directly holds 1,399 shares of Common Stock and (v) 150,044 shares of Common Stock in the name of Peter Y. Chung are held for the benefit of Summit Partners, L.P.

By virtue of the affiliate relationship among the Entities and by virtue of Mr. Mannion’s and Mr. Chung’s membership in the two-person investment committee of Summit Partners, L.P., each of the Reporting Persons may be deemed to own beneficially all of the 3,877,890 shares of Common Stock as of December 31, 2022. Each of the Reporting Persons expressly disclaims beneficial ownership of any shares of A10 Networks, Inc., except with respect to shares held of record by such Reporting Person, as provided above.

The filing of this Statement shall not be construed as an admission that any Reporting Person is, for the purpose of Section 13(d) or 13(g) of the Exchange Act, the beneficial owner of any securities covered by this Statement.