Storefront. We have our own headless e-commerce platform, with iOS, Android, and Web clients. We also have our own order management system that mediates between storefront and our ERP (which is commercial SaaS). And a handful of other smaller applications for everything from outbound carrier rate card testing, to customer service tooling & automation (integrated with ZenDesk) and all sorts of other bits and bobs like ETL code, integration layers, marketing tools, etc, etc. We should not have quite this much custom software, but it takes time to migrate the non-strategic sub-systems to commercial solutions — and even then you’d be surprised how much custom software we DO actually need in a business like this.
My role also encompasses many “CIO-like” functions, but my area of expertise is in application development and I look to hire strong leaders in the other areas (or move certain tech domains entirely into other functions — eg our warehouse management system lives within our operations group, and me and my team help in an advisory capacity but don’t “own” the budget or WMS strategy).