Is there any way to limit parallel disk i/o threads for the electrs indexer?

I found out that electrs opens about 15 of [lookup-txo-xx] processes, slowing down the indexing. My disk subsystem has about 150 MB/s throughputs, but with all those 15 threads it's slowing down to 5 MB/s which's insanely slow. Can I just limit the number of parallel i/o threads to 3-5 somehow? That could hugely speed up the indexing process.

Start with the electrs indexer entry point and the code that launches the lookup-txo-xx processes; no repository file or test is named in the issue. Determine whether a configuration setting already controls their parallelism, and consider the work complete when indexing can reliably use a user-selected limit such as 3–5 threads.

Written by the indexing model from the issue text.