Features sometimes disappear in Android without any explanation. Android 11 introduced IORap (I/O Read Ahead Process), a feature that improves app startup times by predicting which I/O will be required and doing it ahead of time. IORap was silently removed in Android 13.
The cool thing about IORap is that app startup times would be improved without developers needing to make any changes to their apps. You can read about how it worked in this blog post from AndroidDev. IORap was also brought up by the Android engineering team during their annual AMA on /r/AndroidDev.
It was brought to my attention the other day (by arter97 on Twitter) that this feature was removed from Android recently. We looked/asked around and couldn’t find out why. If you know why let me know!