Exhibit 10.42

February 9, 2010

Eric Schwartz

Dear Eric:

This letter is an addendum to the international assignment letter you executed
with Equinix Operating Co., Inc. (the “Company”) dated April 15, 2008, as
amended on December 19, 2008 (“Assignment Letter”). The Company hereby agrees to
extend your international assignment to August 1, 2012. Please note that you and
your family will not receive another familiarization visit, temporary living
assistance, moving costs – household good assistance (except the Company will
continue to pay for any temporary warehousing of your furnishings), settlement
allowance, or driver training as discussed in the Assignment Letter, as these
benefits were one time benefits offered only during your and your family’s
initial move to the United Kingdom.

All other terms and conditions of the Assignment Letter will remain in effect
through August 1, 2012.

Please signify your acceptance of the extension of your international assignment
under these terms and conditions by signing the duplicate enclosed copy of this
letter and returning to me by February 19, 2010.

 

Yours sincerely, /s/ Steve Smith Equinix Operating Co., Inc. Steve Smith CEO &
President

Enclosure

Accepted and Agreed

 

  /s/ Eric Schwartz

   

      17-Feb-2010

Eric Schwartz     Date