Sync behavior in blocking operations (at least for processes) that might be time consuming, i.e remote calls like REST, Database queries, or even local processing. This is a bottleneck mainly in quarkus where we rely on the worker pool (limited threads) for blocking operations.

Provide performance tests to validate and find bottlenecks.

Example:

start -> rest call to an external service -> rest call to an external service -> end

REST/Database clients already provide reactive / non-blocking APIs but since the engine is blocking, there is no way to use them without blocking.

Analyze possible solutions and come with a design.