The underlying JS engine is, iirc Node based... you can definitely use&#x2F;utilize C&#x2F;C++ modules&#x2F;packages there... and very little is stopping someone from doing that.  There are also child processes (and iirc, web-workers).  While a Process !== a thread, on some OSes they are more similar or less in terms of creation cost.  RPC&#x2F;Communication channels are another issue combined with message serialization&#x2F;deserialization which is the biggest cost to overcome with this type of model.