My last FAANG team had a soft 4-hour review SLA, but if it was a complicated change then that might just mean someone acknowledging it and committing to reviewing it by a certain date/time. IIRC, if someone requested a review and you hadn't gotten to it by around the 3-hour mark you'd get an automated chat message "so-and-so has been waiting a while for your review".

Everyone was very highly paid, managers measured everything (including code review turnaround), and they frequently fired bottom performers. So, tradeoffs.