Nim threads don&#x27;t share memory. Each has its own GC heap with data exchanged through messages. The lack of thread safety is irrelevant when they can&#x27;t normally get to each others memory. This of course has performance implications for certain types of parallelism. Nim optimizes for a model where workers don&#x27;t have to have high speed, high volume inter-communication. If you need shared memory it is up to you to add it along with whatever safety measures you need.