SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84f513a9e62ad948a22472e0f7dd32ff6a161b846bdeecdebfc988241ebc3b1f' 
  AND token = 'zLXwJHdVUA3UBjsvjcnnlzBM9dMV2Gxh5o0m+AXqwyY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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