Delete all duplicated entries where multiple columns duplicates match
The easiest way to remove duplicates is to join the table with itself:
DELETE z.* 
  FROM kraken AS w
  JOIN kraken AS z ON z.exchange_pair = w.exchange_pair
                  AND z.timestamp = w.timestamp
                  AND z.id &gt; w.id -- or what primary key you have
;

All duplicates will be deleted except one with the lowest id.