The queries individually are not a huge issue, and concurrent connections are of course allowed, but the combination of both are creating general slowdown on labsdb1003. Note that each query is reading nearly a billion rows.
MariaDB labsdb1003 heartbeat > SHOW PROCESSLIST; 44:| 433954297 | s51434 | 10.68.16.121:33571 | dewiki_p | Query | 14630 | Queried about 713090000 rows | select distinct p.page_id,p.page_title,p.page_namespace,p.page_touched,p.page_len FROM ( SELECT * fr | 0.000 | 45:| 433958543 | s51434 | 10.68.16.121:33602 | dewiki_p | Query | 14323 | Queried about 698630000 rows | select distinct p.page_id,p.page_title,p.page_namespace,p.page_touched,p.page_len FROM ( SELECT * fr | 0.000 | 46:| 433971317 | s51434 | 10.68.16.121:33684 | dewiki_p | Query | 13517 | Queried about 574170000 rows | select distinct p.page_id,p.page_title,p.page_namespace,p.page_touched,p.page_len FROM ( SELECT * fr | 0.000 | 47:| 433978766 | s51434 | 10.68.16.121:33844 | dewiki_p | Query | 13034 | statistics | select distinct p.page_id,p.page_title,p.page_namespace,p.page_touched,p.page_len FROM ( SELECT * fr | 0.000 | 48:| 433991549 | s51434 | 10.68.16.121:33978 | dewiki_p | Query | 12208 | Queried about 553510000 rows | select distinct p.page_id,p.page_title,p.page_namespace,p.page_touched,p.page_len FROM ( SELECT * fr | 0.000 | 52:| 434079943 | s51434 | 10.68.16.121:35384 | dewiki_p | Query | 6265 | statistics | select distinct p.page_id,p.page_title,p.page_namespace,p.page_touched,p.page_len FROM ( SELECT * fr | 0.000 | 53:| 434085600 | s51434 | 10.68.16.121:35584 | dewiki_p | Query | 5869 | Queried about 183500000 rows | SELECT pl_namespace,pl_title from page p0,pagelinks pl0 WHERE p0.page_namespace=0 AND p0.page_title | 0.000 | 54:| 434085671 | s51434 | 10.68.16.121:35585 | dewiki_p | Query | 5864 | Queried about 183570000 rows | SELECT pl_namespace,pl_title from page p0,pagelinks pl0 WHERE p0.page_namespace=0 AND p0.page_title | 0.000 | 55:| 434085923 | s51434 | 10.68.16.121:35586 | dewiki_p | Query | 5848 | Queried about 183450000 rows | SELECT pl_namespace,pl_title from page p0,pagelinks pl0 WHERE p0.page_namespace=0 AND p0.page_title | 0.000 | 60:| 434145817 | s51434 | 10.68.16.121:36509 | dewiki_p | Query | 1151 | Queried about 5580000 rows | SELECT pl_namespace,pl_title from page p0,pagelinks pl0 WHERE p0.page_namespace=0 AND p0.page_title | 0.000 | 66:| 434151494 | s51434 | 10.68.16.121:36593 | dewiki_p | Query | 736 | Queried about 3440000 rows | SELECT pl_namespace,pl_title from page p0,pagelinks pl0 WHERE p0.page_namespace=0 AND p0.page_title | 0.000 | 67:| 434151846 | s51434 | 10.68.16.121:36602 | dewiki_p | Query | 711 | Queried about 3330000 rows | SELECT pl_namespace,pl_title from page p0,pagelinks pl0 WHERE p0.page_namespace=0 AND p0.page_title | 0.000 | 69:| 434152507 | s51434 | 10.68.16.121:36614 | dewiki_p | Query | 676 | Queried about 3160000 rows | SELECT pl_namespace,pl_title from page p0,pagelinks pl0 WHERE p0.page_namespace=0 AND p0.page_title | 0.000 | 124 rows in set (0.00 sec)