Hey,
maybe you had too many tasks in your queue due to the usage of Ajax which are now putting high load on your system until those are processed?
Have you tried to research from which component the high load is coming from?
Some additional things i’m seeing which could give additional performance improvements:
Have you considered to update to the recent Server 10.1.0 Release ?
I think the memcache.distributed isn’t required for your setup as long as you don’t have multiple systems accessing the same redis cache.
According to the documentation below APCu is recommended for small / home systems.
Maybe using unix sockets like described in the documentation below could avoid the overhead of a TCP connection: