If your company relies on SAP ERP as a system of record, and you want to add eCommerce functionality so your customers can order online, there is always a question of the best way to introduce eCommerce functionality to SAP. A traditional approach is to use an existing eCommerce platform (like Hybris, Magento, Shopify etc.) that solves the eCommerce part of the equation. Most off-the-shelf eCommerce solutions are designed to be self sustaining and provide their own databases to store product catalogs, pricing and orders. When integrating with SAP they usually rely on independent solutions to shuttle data (products, prices, orders etc.) between SAP and the eCommerce platform’s internal database. While some eCommerce applications themselves can be Open Source (like Magento), the integration with SAP is usually a custom, proprietary, “bolt on” solution built by 3rd parties. This traditional approach is often referred to as “Outside SAP ⇨ In” eCommerce as the eCommerce capabilities are provided outside SAP and customers, orders etc, are pushed into SAP via some sort of synchronization mechanism.
Both approaches have their advantages and are better suited for a particular business environment.
"Inside-Out" systems are great for small to medium sized SAP-centric companies as they require no external hosting and can be managed day-to-day by internal SAP resources. They generally require less maintenance as any changes to order processing and pricing logic in SAP are immediately reflected in the eCommerce web site (internally, when placing orders, they usually rely on real-time SAP order simulation so any business rules that are available to SAPGUI user executing VA01 are automatically taken into account).
“Outside-in” solutions are a good fit for larger companies whose systems are already distributed and data (e.g. CPQ, payments, shipping, etc.) already lives across multiple systems and can afford resources for hosting and managing data synchronization between them. Also, if your company is driven by marketing (as in many B2C companies are) and requires rapid changes to the web site, Outside-In architecture usually offers a better flexibility to adapt the site look and feel to the latest approach your marketing department wants to try.