There is no definitive answer to this question as it depends on a number of factors, including the hosting environment, the type and number of products, the number of concurrent users, and so on. However, here are some general guidelines that may help:
Choose a fast and reliable hosting provider. This is particularly important for WooCommerce stores, as they tend to be very resource-intensive.
Optimize your website for speed. This includes using a caching plugin, optimizing your images, and using a content delivery network (CDN).
Use a WooCommerce-specific caching plugin. There are a number of these available, and they can help to significantly improve performance.
Consider using a product import/export plugin. This can be helpful if you need to import a large number of products or product variations.
Make sure your WooCommerce settings are optimized. This includes things like enabling AJAX for add-to-cart buttons, disabling the cart fragments feature, and so on.
Keep your WooCommerce up to date. Newer versions often include performance improvements.
Follow standard website performance best practices. This includes things like using a content delivery network (CDN), minifying your CSS and JavaScript files, and so on.
If you're still having performance issues, consider switching to a faster theme or using a lighter-weight plugin.
Ultimately, the best way to ensure your WooCommerce store can handle a large number of product variations is to test it under real-world conditions. This means setting up a test store with a large number of products and variations, and then watching how it performs under realistic load.