SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '568a729d09abb3404bb4bbf2716b05e97196844923a84f83c6e6bf823125af44' 
  AND token = '/sQ3ZEqcRrzZL63+J8acBeBdCawy7PJ9q4fDKhuJL5M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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