JVM

Java

async-profiler and YourKit: JVM Performance Profiling in Production

async-profiler is a low-overhead sampling profiler for JVM applications that generates flame graphs showing where CPU time is spent. YourKit is a commercial profiler with deeper analysis. This guide covers attaching both profilers to running JVM processes, reading flame graphs, finding memory leaks, and profiling in production environments.

Scala

Akka TestKit: Testing Actors, FSMs, and Actor Lifecycles in Scala

Akka TestKit provides specialised tools for testing actor-based systems: TestProbe intercepts messages, expectMsg asserts on received messages with configurable timeouts, and TestFSMRef exposes FSM internals for white-box testing. This post covers every layer from simple unit tests to complex multi-actor scenarios. Testing actors is fundamentally different from