Is it possible to compare timestamps between rows?
The problem is, when you GROUP on user,foo,bar you are not able to get a list of each of those times to compare. 

Something like this might work, but no idea on the performance on a large table. You might want to only do this on a subset (ie tuples just from the last 30 days) 

SELECT A.*,B.time FROM reqs A
INNER JOIN (SELECT user,foo,bar,time FROM reqs) B 
 USING (user,foo,bar)
WHERE A.time!=B.time AND ABS(TIMESTAMPDIFF(SECOND, TIMESTAMP(A.time), TIMESTAMP(B.time))) &lt; 60
GROUP BY A.user,A.foo,A.bar,A.time;