We can help you with that, we have worked with Quintessential Fashion Direct with over 50,000 products (http://www.quintfashiondirect.com/) and Quintessential Beauty Direct (http://www.quintbeautydirect.com/) with over 35,000 product each loading thousands more each day. There are issues with performance and you need to be running 1.6 or above, but there are optimisations that can be run such as php compiling, dual cache, memcache, read database, customised index management settings and load balancing.
1. Will 20000+ products slow down Magento like a snail no matter how we optimize the speed? Any sample store here runs over at least 10000+ items and it runs fine?
- Yes it will become very slow, however with mutiple optimizations you will achieve instant page loads without full page caching
2. Should I theme it first or should the speed optimization go first?
- They can be done in any combination, we believe in non-code based optimisation and work with EverestCloud to host high-performance sites on Amazon Web Services (AWS)
3. Should I hire an expert to optimize the site or just buy any existing extension with a good reviews on it? What’s the differences?
- There is one thing we can guarantee, no one extension will work, it will require a combination of 5-10 different performance enhancements but it will be an industry leading site at the end
4. Should I consider any other open source platform like OpenCart?
- Magento has multi-currency, multi-language and a large help base on an enterprise level architecture. The other carts are more business based to simplify implementation, Magento is more technical based which is what you need when you are dealing with high volumes of products, there will be a lot of disagreement about this however we have worked with companies from Renault to the smallest web sites.
The most important functions that we need are:
1. Batch product CSV upload
- The internal CSV load in the new versions is incredibly fast, 100s to 1,000s of products a minute, you can also develop custom load code instead however this is slower, 20 products a minute for example although it is automated
2. Customer profile and purchase history
- Built in to the admin control panel
3. Fast loading speed
- With the optimisations as above, yes
4. PCI and DSS Compliance for security
- Yes, however given the security issues in the past years it is normally best to use the merchant card providers card storage facilities so you can deal with business at and and not the security aspect
5. User friendly control panel
- Yes, built in to Magento
We hope that helps.