The upstream admin gateway deterministically truncates the first per-row
getUserById that immediately follows a request's auth check, yielding an
empty body the per-call retry cannot clear — so a couple of tunnel rows
showed owner_email '—' on every load regardless of retry or concurrency.
Replace the per-row getUserById fan-out with a single bounded listUsers
scan (same transient retry) that builds an id->email map and stops early
once every owner on the page is resolved. A single listUsers read does not
hit the truncation pattern, eliminating the dashes. Remove the now-unused
mapWithConcurrency helper and OWNER_EMAIL_CONCURRENCY constant.
A large concurrent burst of getUserById calls during the tunnels-list
email enrichment self-inflicts an upstream throttle (truncated/empty
bodies) that even the per-call retry can't fully escape, intermittently
rendering owner_email as '—'. Add mapWithConcurrency and resolve owner
emails at most a few at a time so each lookup stays inside the throttle
allowance; retry + null fallback preserved.
Gerhard Scheikl