It has a single writer transaction mutex, yes. But it's a process-shared mutex, so it will serialize write transactions across an arbitrary number of processes. And of course, read transactions are completely lockfree/waitfree across arbitrarily many processes.
As for working set size, that is always merely the height of the B+tree. Scans won't change that. It will always be far more efficient than any other DB under the same conditions.
> As for working set size, that is always merely the height of the B+tree.
This statement makes no sense to me. Are you using a different definition of "working set" than the rest of us? A working set size is application and access pattern dependent.
> It will always be far more efficient than any other DB under the same conditions
That depends on how broadly or narrowly one defines "same conditions" :-)
As for working set size, that is always merely the height of the B+tree. Scans won't change that. It will always be far more efficient than any other DB under the same conditions.