Why mem pressure is showing 99% all of sudden?

We could suddenly see that the memory pressure is 99% all of sudden for our PRODUCTION cluster.

I could not sense any major activity in application for now.
What could be the reason for this.

Also, the application is not responding due to this as DB queries are failing.

Please respond.


[Thread moved from Found, as this is about generic usage of Elasticsearch, and not an infrastructure problem]

Please look into the messages we have sent, particularly about the pitfalls about extremely high bool.max_clause_counts and their effect on filter caches and memory usage.