#33🚀 DeploymentCareer-Ending

Running Destructive Changes Before Deploying Replacements

“Delete the old stuff AFTER the new stuff is live. Not before.”

What Happened

Client wanted to rename a custom object. I ran destructive-changes.xml to remove the old object first, planning to deploy the new one right after. But the old object had lookup relationships, validation rules, and Flows pointing to it. The destructive deploy cascaded. Fields vanished. Flows broke. Validation rules errored. It took three days and a partial data recovery to fix what should have been a 20-minute rename.

The Wrong Way

<!-- destructive-changes.xml - DON'T RUN THIS FIRST -->
<?xml version="1.0" encoding="UTF-8"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
  <types>
    <members>Legacy_Application__c</members>
    <name>CustomObject</name>
  </types>
  <version>59.0</version>
</Package>

# Destroy first, ask questions later
sf project deploy start -d empty-dir --post-destructive-changes destructive-changes.xml -o production

The Right Way

# Step 1: Deploy the NEW object and all references first
sf project deploy start -x manifest/package-new-object.xml -o production --test-level RunLocalTests

# Step 2: Migrate data from old to new
sf apex run -o production -f scripts/migrate-legacy-to-new.apex

# Step 3: Update all Flows, validation rules, lookups to point to new object
sf project deploy start -x manifest/package-updated-refs.xml -o production

# Step 4: Verify everything works for a week

# Step 5: NOW destroy the old object
sf project deploy start -d empty-dir \
  --post-destructive-changes destructive-changes.xml \
  -o production

The Lesson

Destructive changes are irreversible. Deploy replacements first, migrate data, verify everything, then delete. Never the other way around.

Share this mistake on X

Don't make this mistake.

Hire someone who already did.

View Consulting →

#32 Deploying Apex Without Including the Test Class Skipping Sandbox and Deploying Straight to Production #34

Enjoyed this? Get more like it.

Glen's Musings — AI, investing, and building things. Occasional. Free.