I'm very new to Elasticsearch. I'm exploring the possibility to use Elasticsearch for searching eCommerce orders, products and related data. Right now we have around 15 million orders in our SQL Server database, and each of them has related data such as order rows, customer data and so on. We expect the number of orders to grow a lot coming years. I want, if possible, to keep all orders searchable no matter how old they are. The number of searchable fields (fields in documents) will be limited, but I cannot say how large a document will be at this moment.
My question is how I should go about creating indexes for this data to make sure I don't end up with indexes that are too large (over the 50 Gb recommended limit)? Should I index the orders by year, or any other time period, and search multiple indexes? Is there a better way?