Does Metorik hurt my store's performance/speed?
The short answer: not really - but, it depends.
WooCommerce has a few little performance issues in its API that can cause issues for large stores. These are mostly solved by the Metorik Helper plugin - you can read about that here. You should always keep it active.
But for big stores that are in the 10,000+/orders a month range, there can be some issues in your site due to WooCommerce's webhooks.
When an order is made on your store or a product is updated, WooCommerce sends a 'webhook' to Metorik so Metorik knows about the new order or product change. If you have a lot of these events happening, it results in a lot of webhooks, which can slow down your site a bit.
If you notice an issue like this, it's possible to disable the Metorik webhooks in your dashboard under (WooCommerce > Settings > API > Webhooks). Metorik has a backup method that runs every hour that will get all the missing or out of date data very quickly with very little/no performance impact at all, so everything will still be synced (but just delayed an hour at most). There's also a 'Force Sync' tool you can run at any time from your Metorik store connection settings.
However, Metorik's real-time syncing is a great feature and the webhooks really shouldn't impact your site unless you're in the 10,000+/orders a month range. So we'd highly recommend you contact your host to see what is causing the performance issues (if you're having any).
Any questions about this at all? Please contact us on the live chat or by email. We'd be very happy to investigate any issues you're having, chat about them, and provide possible solutions and explanations. There are plenty of stores using Metorik that have 10,000's of orders a month and have no issues, so it's definitely possible to fix any issues you're having :)
Note: WooCommerce 3.3 (released end of January, 2018) improves webhook performance quite a bit. So if you're noticing issues with them on your site, please try updating.