Yeah this can be a hard problem to solve. In most managed languages to 'properly' deal with it you typically need to accept locking on some level (like with Co

Yeah this can be a hard problem to solve. In most managed languages to 'properly' deal with it you typically need to accept locking on some level (like with ConcurrentDictionary in C# or ConcurrentHashMap in Java). One semi-elegant (yet internally complex) solution I've seen; in C# there is the language-ext library. All the collection types are structs (value types where things like .Add() return a new struct) however the struct itself just holds an implementation to a class. This works well from a user standpoint but the internals of the code is... interesting to say the least and can still lead to a lot of allocations if you're not careful.