SELECT products.user_id, products.created
FROM (

SELECT user_id, created, IF( @prev <> user_id, @rownum :=1, @rownum := @rownum +1 ) AS rank, @prev := user_id
FROM products t
JOIN (

SELECT @rownum := NULL , @prev :=0
) AS r
ORDER BY t.user_id
) AS products
WHERE products.rank <=2
ORDER BY created