Hey! So I was making my mob farm and mobs are BARELY spawning. I made sure my afk spot was 24 blocks away from the farm and the ground was lit up by torches. Here's the mob farm design I used.
There's a water mecanism too if that helps. When mobs spawn they spawn 1 by 1, not in groups.
Here's an image.
EDIT : I fixed the issue, theres caves under my afk spot, I put it a bit higher.