There are both memory and performance considerations. For a server&#x2F;db web application this may not be a problem, but for e.g. some logic in a game engine that runs every frame on a mobile device, then using 16 extra locks per map for example isn&#x27;t a good idea. Nor is having 5% performance overhead.<p>I can agree with an argument that thread-safe should be <i>default</i> and specialized&#x2F;fast collections should be optional though.