The index stats Lua interface is very slow: ~50 indexes in the enWS Monthly Challenge are hitting the script timeout limits occasionally.
Interestingly, the culprit is not the DB lookups of the stats (which are fast, due to being cached in the pr_index table), it's the template dependency on every page in the index:
```
68.20% 11140.528 13 - ProofreadPage\ProofreadPageLuaLibrary::doGetIndexProgress
68.06% 11118.235 13 - ProofreadPage\ProofreadPageLuaLibrary::addTemplateDependencyOnAllPagesInIndex
65.39% 10680.764 6475 - ProofreadPage\ProofreadPageLuaLibrary::addTemplateDependencyOnPage
62.97% 10286.126 14108 - Title::getArticleID
58.04% 9480.184 9218 - LinkCache::addLinkObj
57.52% 9395.358 9218 - LinkCache::getGoodLinkRow
53.44% 8728.561 9218 - LinkCache::getGoodLinkRowInternal
44.32% 7239.807 6941 - Wikimedia\Rdbms\DBConnRef::__call
43.43% 7094.190 6741 - Wikimedia\Rdbms\Database::select
42.84% 6997.686 6514 - Wikimedia\Rdbms\DBConnRef::selectRow
42.68% 6972.202 6453 - LinkCache::fetchPageRow
42.62% 6961.912 6528 - Wikimedia\Rdbms\Database::selectRow
38.59% 6303.721 6746 - Wikimedia\Rdbms\Database::query
38.09% 6222.709 6746 - Wikimedia\Rdbms\Database::executeQuery
34.17% 5581.356 6746 - Wikimedia\Rdbms\Database::executeQueryAttempt
28.22% 4609.597 6453 - section.query-m: SELECT page_id,page_len,page_is_redirect,page_latest,page_restrictions,page_content_model FROM `page` WHERE page_namespace = N AND page_title = 'X' LIMIT N [TRX#b3d87ae539]
```
We should see if we can speed this up a bit (or a lot!)