The SaaS migration checklist: Moving without downtime

Migrating a Cape Town business from one SaaS platform to another is the highest-stakes moment in the engagement. The client is nervous, customers are watching, and the old vendor is often hostile. We've done it 30+ times and learned the hard way what works. Here's the checklist that keeps us at zero customer-visible downtime.

Discovery and data audit (week 1). Before anything else, audit what you're migrating. Get a full export from the current vendor — customers, orders, invoices, products, bookings, support history, AI logs. If the vendor doesn't offer export, treat that as a red flag and require it as a precondition of the engagement. Map every record type to its new home in Apex-OS, and identify any field transformations needed (date formats, currency rounding, status enums).

Parallel backfill (week 2). Set up a nightly job that pulls the latest export from the old vendor and backfills into a staging database. Run this for at least 7 days before the cutover. The goal is to surface every edge case — malformed records, missing fields, broken foreign keys — while you still have time to fix them. Mother City Logistics's migration surfaced 47 records with malformed addresses that the old platform silently swallowed; we fixed them all before launch.

Side-by-side run (week 3). Run both platforms in parallel for at least 7 days. New orders go to the old platform; the new platform mirrors them via the backfill job. Sanity-check revenue totals, customer counts, and inventory levels daily. When the numbers match for 5 consecutive days, you're ready to flip. If they don't, you've found a migration bug while it's still invisible to customers.

Cutover and rollback (a weekend). Cut over on a Saturday night when traffic is lowest. DNS is flipped, the old platform goes read-only, and the new platform opens for new orders. Keep the old vendor on a 90-day retention contract — you'll need access to historical records for SARS, dispute resolution, and the inevitable customer email asking about an order from 6 months ago. Have a documented rollback plan: if anything critical breaks in the first 24 hours, DNS flips back and you're live on the old platform within 5 minutes.

Post-migration support.