Our architecture is:
We use apache velocity as the templating engine for shopper pages as it works better in a clustered environment and JSP for the admin pages. We have UI,BA,BO and DAO layers.
We have great support for multiples stores and multi tenants. Our master catalog module lets you manage hundreds of stores from 1 store. Child stores can then subscribe to products and be updated when the master is updated.
Looking for marketplace solutions? We can do that too.
You get full source code and you can modify it. Because we use spring you can wire in your changes in spring xml files and not fork the code. We also have a module subsystem that lets you create modules that work with the code but are not dependent on it.
Unlike other solutions Dev , QA, UAT servers are free. We only change licenses for production servers. A typical production setup is 1 prod preview server where you manage the catalog, and templates and can make test orders and a cluster of shop servers. You can put all on 1 server or spilt them up as your load increases.
We have lots of experience with the AWS EC2 cloud and have tools that autoscale up and down so that you can idle on 1 server at 3am then automatically launch as many shop servers as you need when the load increases. If you need to use VPC's, ELB's, RDS, Cloudfront and other AWS systems we can get your team up to speed fast and setup your prod servers quickly or provide detailed docs for your team to do this.
We have also solved many challenges with large catalogs as we can do incremental solr rebuilds, incremental publishing and we also work with cloud front and akamai.
Do you need advanced ratings and reviews? Realtime Inventory? and Simple ERP integration? PCI Compliance? We have a very deep solution.
If you need advanced search we can of course do faceted search but also search as you type (auto suggest) and 'did you mean' search spell checking.
We have teams that have put many large sites live and can support with with high load critical sites or sites with large catalogs.
If you would like a technical demo contact us. You can also get a good over view of some of our capabilities in the 6 minute video below.