SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '319c9f3ac489e65f7a6039314f63fc621336555d81b544c528b47309adf8cc90' 
  AND token = 'SDuWhmmCIhdZCBy+qzGZXnwsXydUHhIWY0FENAMIdlg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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