Hello, Need help regarding query laning. How historical resources(threads) are used in case of query laning. Let's suppose we have two lane, fast and slow lane. fast lane have 70% threads of borker and slow lane 30%. 1. If only one query running at that time in either of the lane. how historical threads will be used? will all historical thread will be used ? 2. If one only query running in slow lane(take around 10 sec to complete) . while running this query, one query comes in fast lane. how it will impact to slow lane query. will slow lane query get slow down ?

To my knowledge -- The Historicals do not participate in query laning or priority -- that is only done at the Broker level and to determine which query is run next. Any query can access and or all Historicals that have the data that the query needs. Separately you can tier the Historicals in a couple of different ways, but not tied to the Broker query laning or priority.

@John Kowtko is thought it matters for historicals too. See: https://medium.com/@kyle.hoondert/query-prioritization-in-apache-druid-79f2023fc1f2

My bad ... I should have said query laning only. I am not that familiar with query priority ... although Kyle's blog explains he concept nicely 🙂