Hi,

There are no hard "product data limits." Many customers have live implementations that range upwards to 500k and above catalog entries. However, if you're going to have a large catalog, around 500k or more, there are performance considerations. 

Here are a few general guidelines you can follow:

• Implement an enterprise level search provider (like Solr) which will be able to efficiently index you large catalog.
• Eliminate or reduce the number of actual calls you make to the product catalog or database when returning product information during the browsing, search, or checkout processes.
• Search is the critical element with large catalogs, because how you return that search data to you users will determine the response time.

In addition to what Richly has already stated, you should also ensure that you have a good maintenance plan in place.

• Having a scheduled job to re-index the product catalog regularly
• Database maintenance plan to update table index

If you are dealing with a large number of products and their associated data you may want to investigate whether table partitioning will help improve performance.