Fetch accounting for a RangeByteSource: how many range requests were
issued and how many bytes actually crossed the wire, versus how many the
caller asked for. The gap between bytesFetched and bytesServed is the
over-read imposed by block alignment (a real HTTP-Range / OPFS-block store
can only fetch whole blocks); a small gap means the access pattern has good
locality — the property an index-first open (M4) leans on.
Fetch accounting for a RangeByteSource: how many range requests were issued and how many bytes actually crossed the wire, versus how many the caller asked for. The gap between
bytesFetchedandbytesServedis the over-read imposed by block alignment (a real HTTP-Range / OPFS-block store can only fetch whole blocks); a small gap means the access pattern has good locality — the property an index-first open (M4) leans on.