Shipr app provides the option to sync the inventory of all FBA products from Amazon to Shopify anytime you request.
To sync the products go to Shipr dashboard > Settings > Sync > Hit Sync-Now button.
Only the matching SKUs will be synced. This ensures that the stock levels on Amazon and Shopify are the same and you don't have to manually update them each time when you restock on Amazon FBA.
Fast-sync is available on Pro Plan only.
To update the stock levels of ALL FBA products check Anytime-sync option.