SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f82c799364ea6c91c98fda3f70e87bebcd55ec9d231842e58c287e39eb9d819' 
  AND token = '6vgPNdRH3hIPbRg0E0SXaEenDffrixR/5Qztf59TgEo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}