SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '340336488aedce5ddc82b71b85f8687d002a48a1312fc245328d76242ef906ad' 
  AND token = '95keFfS4qbXHUmMUdKpBRBJkfN/pls8CQfTUtXjKv40=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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