"I don't think this will upset the balance of what's going on in the Eastside. Although, we've seen a moderate slowdown in the velocity of Eastside leasing, rates are at an all-time high, and there's still a demand for space there," says Aigner. The Collier exec also noted that already interested parties were looking at sub-leasing some the high-quality space that will come available in the move.

In a move of 1,700 Product Support Services employees and operations from leased space in Bellevue to buildings owned by Microsoft, the technology giant will relocate 340,000 sf—some say up to 440,000 sf—of offices. In a submarket with 21 million sf of leasable office space, it's enough to nudge vacancy rates from .77 at the end of the third quarter to about 2.2% today. Microsoft says it owns approximately 4.87 million sf of space on the Eastside and, while it does not publicize the total amount of Eastside space it occupies, sources estimate it at 8.4 million sf.

Microsoft will be leaving behind space at Bellevue Place in downtown, Ridgewood Corporate Square on NE 1st, Bellevue Court on 114th Ave. NE, and Corporate Campus east on 112th Ave. SE. Offices at those locations, and possibly at Lincoln Plaza on SE 6th St., will be moved into new buildings on Microsoft's campuses in Redmond and its recently constructed Sammamish Park Place complex in Issaquah.