I have used the standard 112k list for a test for JFB and generating a debug file. Normaly I use a list of 3.6 million blocked domains (my own Pihole running on a PI3).
My problem is that my family uses a PiOne with 500 MB RAM with a list of 2 million domains. They still are on PiHole 4.11 which performs good. For test purposes I have done an update from 4.11 to 423 on my test PiOne. See the first message of this topic. With the same Pihole settings and the same addlist file, the memory usage of FTL grows from 254 MB to 470 MB (55% to 94% memory usage)! With 94% I can not advise my family to update their Pihole.
And also see FTL V4.2.2/4.2.3 consumes nearly 2x more memory then V4.11 for my own PiHole running on a PI3. The FTL proces uses 341 MB in version 4.11, now it’s 616 MB. Nearly 2 times more. Memory usage grows from 37% to 66%. With the same addlist and nothing changed in configuration.
MJMW has a same problem with his huge addlist; see Problem since update to 4.2.*
Why this high memory usage after the update? I think it's not only for the shared memory to the API, but that something is going wrong in storing the gravity.list into memory.