You can look into increasing the hardware and memory at both apache drill as well as Helical insight so that you get better performance.
Apache drill heap memory can be increased as well as number of cores of apache drill server for better performance at drill level. For increasing heap memory where-ever you have installed apache drill there is a “bin” folder and that folder contains a file drill-env.sh Edit this file and over there the memory is mentioned like max min etc. Please increase it. Then restart of drill is required
In a similar way you can increase the JVM and hardware of helical insight also. Follow this blog : How to Increase JVM Memory in Helical Insight Application?