Graphic snapshot:

The green graph is heapUsed.
Black - heapTotal.
Blue - RSS.
HeadUsed has the shape of a saw: it grows and falls, i.e. memory is cleared. HeapTotal and RSS is growing constantly.
If you terminate all connections, then heapUsed will drop to 92mb, and HeapTotal and RSS will remain at ~ 1GB.
Schedule:

Why? Sign of a leak?
Thank.