Yes, it is possible to repair the back glass on an iPhone XS. Here are a few key points about repairing iPhone XS back glass:

• The back glass is a separate component from the rear aluminum housing, so just the glass can be replaced. However, getting to the back glass requires completely disassembling the phone.
• Replacing the back glass is very challenging and labor intensive due to the tightly packed internal components. The repair requires heat and precision tools to detach and reattach adhesives and flex cables.
• It's highly recommended to have the back glass replaced by an experienced phone repair technician. Professional services like iCracked employ technicians or Mobile Repair Doctor that have specialized training and tools for iPhone back glass repair.
• Repair costs can range from $100 to $300+ depending on factors like technician fees and replacement glass quality. High quality OEM-grade glass will provide the most authentic, long-lasting repair.
• Visible imperfections in the back glass like cracks or scratches will be eliminated with a replacement. However, any damage to the aluminum housing itself cannot be fixed with a new glass.

So in summary - back glass replacement is possible on the iPhone XS but quite difficult compared to more modular iPhone models. Unless you have special repair experience, take advantage of professional repair services like iCracked to ensure proper installation and post-repair water resistance.