The `wb_terms_language` index on `wb_terms` is almost certainly not very useful (just ~400 distinct values over 600M+ rows), thus it can probably be dropped for good.
From db1087:
KEY `wb_terms_language` (`term_language`),
[x] dbstore2001.codfw.wmnet 3315
[x] db2089.codfw.wmnet 3315
[x] db2086.codfw.wmnet 3315
[x] db2085.codfw.wmnet 3315
[x] db2084.codfw.wmnet 3315
[x] db2083.codfw.wmnet 3306
[x] db2082.codfw.wmnet 3306
[x] db2081.codfw.wmnet 3306
[x] db2080.codfw.wmnet 3306
[x] db2079.codfw.wmnet 3306
[x] db2075.codfw.wmnet 3306
[x] db2038.codfw.wmnet 3306
[x] db2045.codfw.wmnet 3306
[x] db2052.codfw.wmnet 3306
[x] db2059.codfw.wmnet 3306
[x] db2066.codfw.wmnet 3306
[x] db2023.codfw.wmnet 3306
[] labsdb1001.eqiad.wmnet 3306 (not possible, read-only host: T179464)
[x] labsdb1003.eqiad.wmnet 3306
[x] labsdb1009.eqiad.wmnet 3306
[x] labsdb1010.eqiad.wmnet 3306
[x] labsdb1011.eqiad.wmnet 3306
[x] db1095.eqiad.wmnet 3306
[x] dbstore1001.eqiad.wmnet 3306
[x] dbstore1002.eqiad.wmnet 3306
[x] db1070.eqiad.wmnet 3306
[x] db1071.eqiad.wmnet 3306
[x] db1082.eqiad.wmnet 3306
[x] db1109.eqiad.wmnet
[x] db1110.eqiad.wmnet
[] db1087.eqiad.wmnet 3306
[x] db1092.eqiad.wmnet 3306
[x] db1096.eqiad.wmnet 3306
[x] db1099.eqiad.wmnet 3306
[x] db1100.eqiad.wmnet 3306
[x] db1104.eqiad.wmnet 3306
[x] db1106.eqiad.wmnet 3306
[] db1063.eqiad.wmnet 3306