Not too hard.
Generally, it's a half-day process.
Very smart engineers.
The actual difficulty depends on the group/team that is hiring.
There is no manual QA; test engineers are on par with developers.
Some coding questions
The following metrics were computed from 2 interview experiences for the Splunk QA Engineer role in United States.
Splunk's interview process for their QA Engineer roles in the United States is fairly selective, failing a large portion of engineers who go through it.
Candidates reported having mixed feelings for Splunk's QA Engineer interview process in United States.