I've used a Pi-Hole now for a few years and am a huge fan! Unfortunately after upgrading to version 5, I have found that my cache usage has dramatically dropped.
Previously I would see only 20-40% of all DNS queries being forwarded on from the Pi-Hole. Now between 50-70% of all queries are forwarded.
I've read through the https://docs.pi-hole.net/ftldns/dns-cache/ article but see there's no reason to increase my cache size (I expect that the cache is just expiring records before they're requested again?).
My Pi-Hole is only used at home (11 devices), so I realise it will never see as many repeat DNS queries as you might on a busy network, but regardless there has been a dramatic drop in efficiency.
I'm running Pi-Hole on a Rasberry Pi 2b with Rasbian Lite OS. I have around 770,00 domains on the blocklist (most from EnergizedProtection's "Basic" collated list).
My system has no problems and appears to otherwise be working properly.
This all concerns me as the DNS server the Pi-Hole forwards to (on my Linux-based router) is using DoT to downstream DNS servers which are potentially high latency. I really want caching to be as efficient as possible.
Thank you very much in advance!
EDIT: Moved out of Help Community category as I have a totally standard install
EDIT2: Changed Cache efficiency to Cache Utilisation at Bucking Horn's suggestion