Practice the ROS2 Thread-Safe by Coincidence coding problem in Code Audit. Browser-based execution with automated grading — no local ROS install required. 0% of engineers pass this challenge.
A sensor fusion node uses MultiThreadedExecutor for performance. In your test environment (low load, single core), it works correctly every time. In production (high load, 8-core server), it occasionally produces wrong output. The bug happens 1 in 20 runs and is completely non-deterministic.
The code "works" because with a single-threaded executor, callbacks never overlap. With MultiThreadedExecutor, they can. This is thread-safe by coincidence — not by design.
Find the race condition and fix it.
It is a hands-on Code Audit challenge on SimuCode where you implement and run ROS2 code in the browser with runtime-verified tests.
Open this page, sign in, and solve the problem in the built-in IDE. Your solution is graded against real ROS2 execution checks.
This Hard problem focuses on threading, race-condition, multithreaded-executor skills used in robotics interviews and production systems.