I have a database of sufficient size that it does not fit entirely in RAM, including indexes that also exceed RAM capacity. When performing queries, I observe significant differences in processing time depending on whether the index needs to be read from disk or is already loaded in RAM. I have confirmed using EXPLAIN ANALYZE that the issue stems from index scans.

I measured the speed of loading my index into RAM during a query, which is approximately 2 MB/s. However, my infrastructure theoretically supports disk read speeds of around 900 MB/s.

This issue appears related to the index itself rather than a disk read speed cap. For instance, when I execute 2 parallel queries on different tables, the disk read speed reaches 4 MB/s. Yet, when I execute 2 parallel queries on the same table, my disk read remains at 2 MB/s.

I am working within an Azure VM environment. If additional information is required, I am available to provide it.