SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad9355018dc3714c64a2290d48439ceb61b6e0470c60865dc35fa389e0f71588' 
  AND token = 'tOzCkDwZnZMNJB9TjMy/Kj+VeKmQ+9TXn6viJBgKM7g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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