Headless and composable stacks promise flexibility - and can become a webhook spaghetti nightmare without contracts and drills.
TL;DR
Document SLAs per vendor, run chaos tests on catalog sync, keep a static fallback for browse-only traffic, and version your integration adapters like product code.
How many vendors is too many?
For most mid-market brands, cart + CMS + search + payments is enough to start. Add personalization or CDP when you have analysts who will actually use the data - not because the RFP checklist says so.
What breaks first in production?
Inventory drift, tax rounding mismatches, and refund race conditions. Invest in idempotent webhooks and reconciliation jobs that compare totals nightly.
Launching a new storefront? Sales funnels and conversion plus a commerce discovery call help you scope the stack.