Performance Bottleneck with scala.util.Random in Concurrent Applications

[laserjobs]

Describe the bug Using the global scala.util.Random singleton causes a severe performance bottleneck in multi-threaded applications. All threads must wait their turn for a single, shared lock to generate a random number, creating a "traffic jam" that slows the entire application down.

To Reproduce Steps to reproduce the behavior:

1. Identify code that uses scala.util.Random in a path that is called by many concurrent threads (e.g., a web request handler).
2. Use a load testing tool to send hundreds of concurrent requests to that code path.
3. Use a JVM profiler to monitor the application's threads.
4. See that many threads are in a BLOCKED state, waiting on a lock for java.util.Random.

Expected behavior The application should scale and handle many concurrent requests efficiently, without being slowed down by random number generation.

Screenshots N/A. This is a performance issue observable in a profiler, not a visual UI error.

Environment

• Language: Scala (2.12, 2.13+)
• Platform: Any modern JVM (JDK 8+)
• Context: Most noticeable in multi-threaded server applications (web services, APIs, data pipelines).

Additional context The solution is to replace the slow, global scala.util.Random with java.util.concurrent.ThreadLocalRandom, which gives each thread its own random number generator and eliminates the bottleneck.