Document:

<PAGE>

                                                                   EXHIBIT 10.43
                                              *CONFIDENTIAL TREATMENT REQUESTED.
                         CONFIDENTIAL PORTION HAS BEEN FILED SEPARATELY WITH THE
                                             SECURITIES AND EXCHANGE COMMISSION.

                        FIRST LEASE AMENDMENT AGREEMENT
                        -------------------------------
                          (MEET POINT ROOM AGREEMENT)

          This First Lease Amendment (this "Amendment") is made as of May 23,
                                            ---------
2001, between MARKET HALSEY URBAN RENEWAL, LLC, a New Jersey limited liability
company having an office at 1 Penn Plaza - Suite 1514, New York, New York 10119
("Landlord"), and EQUINIX, INC., a Delaware corporation, having a principal
  --------
office at 2850 Bayshore Parkway, Mountain View, CA 94043 ("Tenant").
                                                           ------

          WHEREAS, Landlord and Tenant have entered into a Lease Agreement dated
as of May 3,1999 (the "Lease") for a portion of the eighth (8th) floor in the
                       -----
building known as [*], Newark, NJ, as more particularly shown and described in
the Lease (the "Demised Premises").
                ----------------

          WHEREAS, Landlord and Tenant desire to amend the Lease as provided
herein.

          In consideration of the mutual covenants herein expressed, and for
other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the parties agree as follows:

1.   ADDITIONAL PREMISES - MEET POINT ROOM SPACE

          Commencing on the date (the "Additional Premises Commencement Date")
                                       -------------------------------------
which is the earlier of (i) June 1, 2001 and (ii) the date that Tenant commences
to conduct business in the Additional Premises, Landlord shall lease to Tenant
and Tenant shall rent from Landlord space enclosed in a lockable wire mesh cage
(cage "G"), (the "Cage") whose area is approximately [*]' x [*]' (the
                  ----
"Additional Premises") in Landlord's "Meet Point Room" which is located on the
--------------------
ninth (9th) floor of the building of which the demised premises are a part, as
shown on Exhibit A attached hereto and made a part hereof and the Additional
         ---------
Premises shall be added to the Premises for the purposes of the Lease and this
Amendment.  Except as otherwise provided herein, from and after the date of this
Agreement, all of the terms, covenants, conditions, and provisions of the Lease
shall apply to the Additional Premises.  The term of the Lease with respect to
the Additional Premises shall be coterminus with the Lease Term for the Demised
Premises; provided that during the sixty (60) days immediately following the
fourth (4th) anniversary of the Additional Premises Commencement Date, Tenant
shall have the right to terminate the Lease with respect to the Additional
Premises only by providing Landlord with written notice within such sixty (60)
day period (the "Termination Notice") of its election to terminate the Lease
                 ------------------
with respect to the Additional Premises.  Following Tenant's delivery of the
Termination Notice, the Lease with respect to the Additional Premises shall
terminate as of the

________________

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.
<PAGE>

date set forth in the Termination Notice.  Tenant's failure
to deliver the Termination Notice within such sixty (60) day period shall be
deemed Tenant's election not to terminate its Lease with respect to the
Additional Premises.

2.   USE
          Tenant shall have to right to install, operate, replace, and remove,
at Tenant's sole expense and risk, wires, communications and security equipment,
cabinets and conduits within the Additional Premises, and a hand scanner at the
Cage entrance, together with the right to install, maintain, operate, and
replace, cables conduits, inner ducts and connecting hardware in order to
interconnect with other entities within the Meet Point Room who have entered
into agreements with Landlord for the use of the Meet Point Room and to
interconnect the Demised Premises including without limitation any of Tenant's
Specialty Equipment, and the Equipment located therein, by using such conduits
and/or core drilling of the slab as are reasonably necessary to make such
connection with the Additional Premises, provided that plans and specifications
for such are approved in advance by Landlord, which approval shall not be
unreasonably withheld conditioned or delayed.  Landlord and Tenant agree that
Section 56 of the Lease shall apply to the Additional Premises.

3.   RIGHT TO RELOCATE ADDITIONAL PREMISES

          Landlord reserves the right to require Tenant, at Landlord's expense,
to relocate within the Building the Cage and connecting conduits, cables, and
equipment associated therewith, provided that any substitute cage shall contain
at least as much area as the Cage from which Tenant is being relocated, shall be
suitable, in Tenant's reasonable judgment, for Tenant's installations, and no
interruption or unreasonable interference in Tenant's operations in the
Additional Premises or Demised Premises occurs.

4.   RENT FOR ADDITIONAL PREMISES

          Commencing on the Additional Premises Commencement Date, Tenant shall
pay monthly rent for the Additional Premises, in addition to and together with
the monthly base rent for the Demised Premises, in accordance with the following
schedule:

<TABLE>
<CAPTION>
                                                                    Monthly Rent for
               From                               To              Additional Premises
               ----                               --              ---------------------
<S>                                          <C>                  <C>
  Additional Premises Commencement Date      June 30, 2002                $[*]
            July 1, 2002                     June 30, 2003                $[*]
            July 1, 2003                     June 30, 2004                $[*]
            July 1, 2004                     June 30, 2005                $[*]
            July 1, 2005                     June 30, 2006                $[*]
            July 1, 2006                     June 30, 2007                $[*]
            July 1, 2007                     June 30, 2008                $[*]
</TABLE>

__________________

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.
<PAGE>

<TABLE>
<S>                                        <C>                   <C>
            July 1, 2008                     June 30, 2009                $[*]
            July 1, 2009                     June 30, 2010                $[*]
            July 1, 2010                     June 30, 2011                $[*]
            July 1, 2011                     June 30, 2012                $[*]
            July 1, 2012                     June 30, 2013                $[*]
            July 1, 2013                     June 30, 2014                $[*]
            July 1, 2014                   September 30, 2014             $[*]
</TABLE>

Landlord represents to Tenant that there shall be no additional charges or fees
payable in connection with Tenant's use and operation of the Additional Premises
other than as set forth herein.

5.   OPERATING EXPENSES FOR ADDITIONAL PREMISES

          Tenant shall pay as additional rent, [*]% ("Tenant's Pro-Rata Share")
                                                      -----------------------
of the total annual Operating Expenses for the Meet Point Room, which shall
consist of the reasonable annual costs of operating, maintaining, repairing,
cleaning, supervising, and securing the Meet Point Room, including, without
limitation, costs incurred by Landlord for electricity (which is not separately
metered to each of the Cage users), gas, security systems, and personnel,
cleaning, and managerial fees and salaries (e.g. engineers, architects) which
are not incurred in the Operating Expenses of the Building ("Meet Point Room
                                                             ---------------
Operating Expenses").  Tenant Pro-Rata Share of Operating Expenses shall be
------------------
payable in monthly installments, together with the base rent.  The Meet Me Room
Operating Expenses shall not be included in "Operating Expenses" as that term is
defined in Article 2 of the Lease.  Landlord and Tenant agree that Operating
Expenses for the Meet Point Room shall not include any monthly base rent payable
or deemed to be payable by Landlord with respect to the space occupied by the
Meet Point Room.

6.   PAYMENT FOR CONSTRUCTION OF MEET POINT ROOM

          Upon execution of this Agreement, Tenant shall pay Landlord a one time
non-refundable reimbursement of $[*] for Landlord's cost in planning,
constructing, renovating, altering, and improving the Meet Point Room,
including, but not limited to, costs and expenses incurred by Landlord for
demolition (including removing existing ceiling), constructing demising walls
(including vapor seal and insulation), flooring, HVAC, electrical work, cages,
overhead racks, racks in ceilings and shafts, lighting, painting, security,
architects' and engineers' fees, construction and supervisory fees, and pre-
action sprinkler. Landlord represents that it will collect the same contribution
from each other user of the Meet Point Room. Landlord agrees to operate,
maintain and repair the Meet Point Room and related facilities in a first class
manner consistent with telecommunications standards of similar facilities .

7.   ADDITIONAL 4" CONDUITS FROM PREMISES TO MEET POINT ROOM

____________________

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.
<PAGE>

          In addition to the conduits permitted to be installed by Tenant under
Section 7 (B) (iv) (1) of the Lease, Tenant shall be entitled to install four
(4) four-inch (4") conduits (with each 4" conduit) from the Demises Premises to
the Additional Premises (the "Additional Tenant Conduits"), subject, however, to
                              --------------------------
all of the terms and provisions of the Lease.

8.   ELECTRIC DEMAND METER

          In the event Tenant elects to utilize electricity in the Meet Point
Room to run its equipment located in the Additional Premises, Tenant shall
install, at Landlord's cost and expense, an electrical "demand" meter which
measures Tenant's electric usage for equipment within the Cage; Tenant shall
pay, within thirty (30) days of receipt of invoice therefor, the actual charges
(i.e. without mark-up by Landlord) for electric service to the Additional
Premises based on said demand meter reading.

9.   LANDLORD ENTRY

          Neither Landlord nor its representatives shall enter the Additional
Premises without giving Tenant 24 hours prior notice.

10.  LEASE TERMS

          Except as amended above, the terms and conditions of the Lease,
including, without limitation, the expiration date of the Lease with respect to
the Demised Premises, shall remain unmodified and in full force and effect.

11.  INCORPORATION

          Except as otherwise provided herein, the terms and conditions of the
Lease shall be incorporated herein with respect to Tenant's lease of the
Additional Premises.

12.  CONFLICT

          In the event of any conflict between this Amendment and the Lease, the
terms of this Amendment shall control.

                        [Signatures on Following Page]
<PAGE>

          IN WITNESS WHEREOF, Landlord and Tenant have signed this Amendment as
of the day and year first above written.

                                        MARKET HALSEY URBAN RENEWAL, LLC,
                                        Landlord

                                        By: /s/ Samuel Jemal
                                           -------------------------------------
                                           Samuel Jemal, Member

                                        EQUINIX, INC., a Delaware corporation,
                                        Tenant

                                        By: /s/ Philip J. Koen
                                           -------------------------------------
                                           Name:  Philip J. Koen
                                           Tenant:
<PAGE>

                  [Graphic Description of Meet-Me Room Layout]

                            [*] MEET-ME ROOM LAYOUT
                               --------------------

_________________
*CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.<PAGE>

                                                                   EXHIBIT 10.44
                                              *CONFIDENTIAL TREATMENT REQUESTED.
                         CONFIDENTIAL PORTION HAS BEEN FILED SEPARATELY WITH THE
                                             SECURITIES AND EXCHANGE COMMISSION.

                           FIRST AMENDMENT TO LEASE

                                LEASE EXPANSION
                                ---------------

THIS FIRST AMENDMENT TO LEASE ("Amendment") by and between NEXCOMM ASSET
ACQUISITION I, LP, a Texas limited partnership ("Landlord"), and EQUINIX, INC.,
a Delaware corporation ("Tenant"), is executed as of the 18th day of April 2000
("Execution Date").

                                  WITNESSETH
                                  ----------

WHEREAS, Landlord and Tenant have heretofore entered into that certain Lease
dated January 21, 2000, (the "Lease"), under the terms of which Landlord leased
to Tenant certain "Premises" located in the "Building" (as those terms are
defined in the Lease);

WHEREAS, Tenant desires to expand the Premises (currently identified as Suite
[*]), to include Suite [*] ("Expansion Space") which includes approximately [*]
"Rentable Square Feet" (as that term is defined in the Lease) in the Building as
outlined on the floor plan attached hereto as Exhibit "A" and incorporated
herein by reference for all purposes.  The Premises, after the addition of the
Expansion Space, shall contain a total of approximately [*] Rentable Square Feet
("Expanded Premises");

NOW, THEREFORE, for and in consideration of the Premises, the mutual covenants
contained herein and in the Lease, and other good and valuable consideration,
the receipt and sufficiency of which is hereby acknowledged and confessed,
Landlord and Tenant hereby covenant and agree as follows:

1.   DEFINED TERMS.  Terms defined in the Lease and delineated herein by initial
     -------------
     capital letters shall have the same meaning ascribed thereto in the Lease,
     except to the extent that the meaning of such term is specifically modified
     by the provisions hereof. In addition, other terms not defined in the Lease
     but defined herein will, when delineated with initial capital letters, have
     the meanings ascribed thereto in this Amendment. Terms and phrases which
     are not delineated by initial capital letters shall have the meanings
     commonly ascribed thereto.

2.   EXPANSION OF PREMISES.  From and after the Execution Date, the Premises
     ---------------------
     shall mean the Expanded Premises and Landlord shall commence the work
     required to demolish the improvements as required to return the Expansion
     Space to shell condition.

________________
*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.
<PAGE>

     Tenant, within two (2) weeks following the Execution Date, shall be deemed
     to commence occupancy of the Expansion Space for the purpose of equipping,
     furnishing, and improving the Expansion Space.

3.   EXPANSION RENTAL COMMENCEMENT DATE.  The Expansion Rental Commencement Date
     ----------------------------------
     shall mean the earlier of June 1, 2000 or the issue date of the Certificate
     of Occupancy for the Premises. Base Rent shall be adjusted accordingly if
     the Expansion Rental Commencement Date is other than June 1, 2000. In that
     regard, after delivery of Expansion Space, Landlord shall have no
     obligation to make any improvements or modifications to the Expansion
     Space.

4.   LEASE TERM.  From and after the Expansion Rental Commencement Date, the
     ----------
     Lease Term shall mean a term commencing on the Expansion Rental
     Commencement Date and continue for one hundred twenty (120) full calendar
     months.

5.   BASE RENT.  From and after the Execution Date, Section 1.1a of the Lease
     ---------
     shall be amended as follows with respect to the amount of Base Rent payable
     with respect to the Expansion Space:

          From the Execution Date until the Expansion Rental Commencement Date,
          Base Rent shall be increased by [*] Dollars ($[*]),

          From the Expansion Rental Commencement Date through May 31, 2002, Base
          Rent shall be increased by [*] Dollars ($[*]) per month,

          From June 1, 2002 through May 31, 2004, Base Rent shall be increased
          by [*] Dollars ($[*]) per month,

          From June 1, 2004 through May 31, 2006, Base Rent shall be increased
          by [*] Dollars ($[*]) per month,

          From June 1, 2006 through May 31, 2008, Base Rent shall be increased
          by [*] Dollars ($[*]) per month, and

          From June 1, 2008 through May 31, 2010, Base Rent shall be increased
          by [*] Dollars ($[*]) per month.

6.   TENANT'S PROPORTIONATE SHARE as defined in Section 1.17 under this Lease is
     ----------------------------
     hereinafter increased by [*] percent in regards to the Expansion Space for
     a total of [*] percent with regards to the Expanded Premises.

7.   RENTABLE SQUARE FEET.  Section 1.1.o of the Lease "Rentable Square Feet" is
     --------------------
     deleted in its entirety and hereinafter replaced with the following:
_______________
*CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.
<PAGE>

          shall mean the Usable Square Feet within the Premises, together with
          an additional amount representing a portion of the Common Areas,
          Service Areas and other non-tenant space on floors one (1) through six
          (6) in the Building.  For purposes of this Lease, the parties have
          agreed that the Expanded Premises shall be deemed to consist of [*]
          Rentable Square Feet and floors one (1) through six (6) of the
          Building shall be deemed to consist of [*] Rentable Square Feet.
          However, both Landlord and Tenant acknowledge that neither of these
          figures was calculated by measuring the Common Areas, Service Areas
          and other non-tenant spaces in the Building and that neither Landlord
          nor Tenant shall have a right to demand remeasurement or recalculation
          of the Rentable Square Feet applicable to the Premises or the Building

8.   EXHIBITS.  The Exhibits attached to this Amendment are hereby incorporated
     --------
     herein and hereby made a part of this Amendment.

9.   COMMISSIONS.  Landlord and Tenant hereby indemnify and hold each other
     -----------
     harmless against any loss, claim, expense or liability with respect to any
     commissions due or brokerage fees claimed on account of the execution of
     this Amendment due to any action of the indemnifying party.

10.  EFFECT OF AMENDMENT.  Except as expressly amended by the provisions hereof,
     -------------------
     the terms and provisions contained in the Lease shall continue to govern
     the rights and obligations of the parties; and all provisions and covenants
     in the Lease shall remain in full force and effect as stated therein,
     except to the extent specifically modified by the provisions of this
     Amendment. This Amendment and the Lease shall be construed as one
     instrument.

IN WITNESS WHEREOF, Landlord and Tenant have executed this Amendment as of the
day and year first above written.

                         LANDLORD
                         NEXCOMM ASSET ACQUISITION I, LP,
                         a Texas limited partnership

                              By: NeXcomm GP I, Inc., a Texas corporation,
                                  Its general partner

                                  By:  /s/ Phillip J. Wise
                                      ------------------------------------
                                  Name: Phillip J. Wise
                                  Title: President
_______________
*CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.
<PAGE>

                                    TENANT
                                    EQUINIX, INC., a Delaware corporation

                                         By:  /s/ Albert M. Avery
                                             ------------------------------

                                         Name: Albert M. Avery

                                         Title: CEO

Exhibit "A" - Designation of Expansion Space
<PAGE>

                                  EXHIBIT "A"
                                  -----------

     To FIRST Amendment to Lease ("Amendment") By and Between NEXCOMM ASSET
          ACQUISITION I, LP, as Landlord and EQUINIX, INC., as Tenant

--------------------------------------------------------------------------------

                        DESIGNATION OF EXPANSION SPACE
                        ------------------------------
                       (For illustrative purposes only)

                  [Graphic of Floor Plan of Expansion Space]

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