Hey there, welcome to the forum.
If you are using DB query reader node the query is executed in the DB - so the performance bottle neck is likely the DB itself that takes time to execute the query.
In the past I had use cases that initially used a DB on MS Azure - as the DB grew and the amounts of data queries returned grew larger, we opted to purchase additional Database Transaction Units, which simply spoken increases cloud resources and consequently make things faster.
Luckily at some stage we switched to a, from my laymans perspective, more performant solution (snowflake).