This seems like a speedy solution for inserts but I'm curious about reads "Indexes tries to reuse as much space as possible, because metadata size is fixed, du

This seems like a speedy solution for inserts but I'm curious about reads "Indexes tries to reuse as much space as possible, because metadata size is fixed, during every write operation, if index finds metadata marked as removed or so, it reuses it - writes new data into that place." I'm curious how this is implemented.