ZIO is a high-performance framework that is powered by non-blocking fibers (which will move to virtual threads under Loom).
ZIO's core execution engine minimizes allocations and automatically cancels all unused computation. All data structures included with ZIO are high-performance and non-blocking, and to the maximum extent possible on the JVM, non-boxing.
benchmarks project has a variety of benchmarks that compare the performance of ZIO with other similar projects in the Scala and Java ecosystems, demonstrating 2-100x faster performance in some cases.
Benchmarks to compare the performance of HTTP, GraphQL, RDMBS, and other ZIO integrations can be found in those respective projects.