为运行服务器的大型XML数据库(10GB - 1TB)创建在线搜索引擎

I have been using Node.js to create a website that will eventually be able to search Google Patent Grant database that provides data in XML format. I've been using MongoDB for the User database, but someone told me that they had a lot of difficulty creating a fast search engine using MongoDB, they also said that it grew very large. What database technology/software should I use in conjunction with Node.js to create an efficient search engine? Would it be a bad idea to have two different database technologies running for one website, e.g. MongoDB and PostgreSQL? I found a technology called Norch on github I have been using Node.js to create a website t