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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df5bb8658c5af884cde699e5d5a0e3c9609030fd40926ff74aaa0e2cf5c09d09' 
  AND token = '8Rf50xGSStuSAKJ4OWEAK8p/dOEcGexqp30KDQnFaFk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}