PostgreSQL internal

index

PostgreSQL uses Lehman-Yao's high concurrency B-tree for standard indexes (https://www.csd.uoc.gr/~hy460/pdf/p650-lehman.pdf).
Along with some PostgreSQL-specific optimizations, these trees provide end users with excellent performance.
The most important thing is that Lehman-Yao allows you to run many operations (reading and writing) on the very same
index at the same time, which helps to improve throughput dramatically.