root@labsdb1012.eqiad.wmnet[heartbeat]> SELECT shard, greatest(0, TIMESTAMPDIFF(MICROSECOND, max(ts), UTC_TIMESTAMP(6)) - 500000)/1000000 AS lag FROM heartbeat.heartbeat WHERE datacenter='eqiad' GROUP BY shard HAVING shard like 's%'
    -> ;
+-------+--------+
| shard | lag    |
+-------+--------+
| s1    | 0.0000 |
| s2    | 0.0000 |
| s3    | 0.0000 |
| s4    | 0.0000 |
| s5    | 0.0000 |
| s6    | 0.0000 |
| s7    | 0.0000 |
| s8    | 0.0000 |
+-------+--------+
8 rows in set (0.001 sec)

root@labsdb1012.eqiad.wmnet[heartbeat]> SELECT shard, greatest(0, TIMESTAMPDIFF(MICROSECOND, max(ts), UTC_TIMESTAMP(6)) - 500000)/1000000 AS lag FROM heartbeat.heartbeat WHERE datacenter='codfw' GROUP BY shard HAVING shard like 's%'
    -> ;
+-------+-------------+
| shard | lag         |
+-------+-------------+
| s1    | 277237.2624 |
| s2    |      0.2624 |
| s3    |      7.2623 |
| s4    |      0.2623 |
| s5    |      0.2624 |
| s6    |      0.2624 |
| s7    |      0.2622 |
| s8    | 278333.2622 |
+-------+-------------+
8 rows in set (0.001 sec)