Not from the tech teams, but I used to be on one of their ops teams working with ERP system. Having quite some experience with SAP before and since I came to the following conclusion:

- Amazon's ERP is way better suited for e-commerce ops than SAP - SAP is much better as an overall ERP system when it comes to include non-ops / warehouse management functions - Amazon's ERP system became hard to adopt and change, meaning it kind of lost the general advantage of a custom system to compared to an off the shelf one - One of the biggest advantages of Amazon's ERP was the full integration of the webshop front end - One of the biggest mistakes Amazon made was to not develop their ERP-webshop systems into a stand-alone product (imagine Shopify with a arguably very good e-commerce ERP system)

Let me elaborate on the last point. The big strength of commercial ERP systems is that they are to large part a readily available collection of best practices from countless companies. By keeping it all in-house Amazon lost that opportunity to learn. IMHO it is not the system that gives Amazon the edge but the way it is used, so incorporating eyternal best practices coupd only help. Also, from the commercial side, it is one gigantic missed opportunity. Imagine a SaaS version of Amazon's ERP running all the shops currently using stuff like Shopifyone that is used by countless small stores as a point of sale software with integrated inventory ans warehouse management functions. That would allow Amazon to create a global, decentralized ERP environment fully integrated into any existing or future fulfillment solutions Amazon has. The upside for Amazon and users of such a system are basically endless.