CPU usage is just an indication (all processes togheter use about 5-10% this is quite low).
The real issue is that after a query time out, dgate, SQL and lsass continue to consume resources more than normal for a long time, maybe 10 to 30mn depending on queries.
And this combines : if several "big" queries comes every 2 minutes for exemple, ram usage by dgate grows exponentially, as the CPU for other processes does beecause each query add a little overload.