SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2943931937572f818f90df35ede6ea95e41642675a16591a71c21876c2624c69' 
  AND token = 'qONsx7AfcjB+GYI6u+JTxnGqiF9hZsLun1oUGlMsbds=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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