The update arrives as build number 40.0.A.5.66 for Xperia XA1, while Xperia XA1 Ultra gets 42.0.A.3.3. The update doesn’t bring the Android 7.1.1 but keeps it on Android 7.0 only.
This is just a security patch and like any other security patch, the update takes care of various security vulnerabilities and brings along fixes to existing bugs. You can also expect performance and stability improvements from the update.
It is advisable to connect to a good Wi-Fi network before downloading the update and keep your handset charged as high as 50 percent.
And, if you haven’t received the update yet, you can check for it manually via the device settings. Go to Settings – About – Software updates.