The operation almost always acquires resources straight-away,
for example a new thread or file access. This means starting
many metadata retrievals in parallel easily causes resource
contention. This problem can be alleviated by limiting the
maximum number of parallel retrievals.
Local testing showed a 20% speedup for local file retrievals
when limited to 5 in parallel. Any more parallel retrievals
did not show any improvement or started getting slower again
the more operations are allowed.
PiperOrigin-RevId: 650674685
b145a9b35e