Major upgrades and replatforms rarely fail because of code. They fail on data, on integrations nobody fully documented, and on cutover plans that assumed everything would go right. These are the lessons I bring to every migration now.
Discovery is part of the migration
Before estimating, list every system that touches the store: ERP, PIM, payments, search, email, shipping, marketing feeds and the spreadsheet someone in operations imports every Monday. Each one is a dependency that can break at cutover. The undocumented ones are usually discovered by asking the people who run the business day to day, not by reading the code.
Upgrade the extensions, not just the platform
On a Magento upgrade, the core version change is often the easy part. Third-party modules, custom code built on deprecated APIs and PHP version requirements make up most of the effort. A technical-debt review at the start (which modules are still needed, which have maintained versions, which should be replaced) makes the estimate honest and the upgrade smaller.
Rehearse with production-shaped data
- Run the full data migration on a recent copy of production, more than once, and time it.
- Check counts and spot-check records: customers, orders, products, URL rewrites and stock.
- Test integrations against their sandbox environments with realistic volumes.
- Load-test the new platform before launch, with caches warm and cold.
Protect SEO and existing links
Map old URLs to new ones and test the redirects. Keep product and category URL keys where possible. After launch, watch for crawl errors and 404 spikes; customers and search engines both remember the old links.
Plan the cutover like a release, with a way back
- Choose a low-traffic window, away from campaigns and peak trading.
- Freeze content and catalogue changes, and agree how orders placed during the window are handled.
- Lower DNS TTLs in advance if DNS is changing.
- Run a written checklist with owners and timings, including smoke tests for checkout and payments.
- Define in advance what “roll back” means and the point after which it is no longer practical.
The people side
A migration is stressful for the client and the team. Clear communication about what will happen, when and who to call does more for a smooth launch than any single technical decision. After go-live, keep the team available through the first busy trading days and hold a short retrospective while the details are fresh.
