SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac5e0576f58eb1a88dbda41e837255cf6742a733004ca07acf6ccea1cd1978d8' 
  AND token = 'Kxvm2lgHqTKLgByYrY1Cz+NtRd9VR8ExZmu0UHRxp+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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