Execute Vercel major re-architecture and migration strategies with strangler fig pattern.
Use when migrating to or from Vercel, performing major version upgrades,
or re-platforming existing integrations to Vercel.
Trigger with phrases like "migrate vercel", "vercel migration",
"switch to vercel", "vercel replatform", "vercel upgrade major".
Migrate applications to Vercel from Netlify, AWS (Lambda/CloudFront/S3), Cloudflare Workers, or traditional hosting. Covers configuration mapping, DNS cutover, feature parity validation, and incremental migration with the strangler fig pattern.
# Create Vercel project
vercel link
# Move function files to api/ directory
mkdir -p api
# Convert each function to Vercel format
# Install Vercel types
npm install --save-dev @vercel/node
Step 3: Migrate Environment Variables
# Export from current platform, add to Vercel
# Netlify:
netlify env:list --json | jq -r '.[] | "\(.key)=\(.values[0].value)"' > .env.migration
# Add each to Vercel with proper scoping
while IFS='=' read -r key value; do
echo "$value" | vercel env add "$key" production preview development
done < .env.migration
# Verify
vercel env ls
Step 4: Incremental Migration (Strangler Fig)
Route traffic incrementally from old platform to Vercel:
// Phase 1: Route /api/* to Vercel, keep everything else on old platform
// On old platform, add a rewrite/proxy:
// /api/* → https://my-app.vercel.app/api/*
// Phase 2: Move static pages to Vercel
// Update DNS for staging subdomain first:
// staging.example.com → cname.vercel-dns.com
// Phase 3: Move production
// Update DNS A record: example.com → 76.76.21.21
Step 5: DNS Cutover
# Add domain to Vercel
vercel domains add example.com
# Verify domain ownership
vercel domains inspect example.com
# DNS records to set:
# Apex domain (example.com):
# A → 76.76.21.21
#
# Subdomain (www.example.com):
# CNAME → cname.vercel-dns.com
#
# Or transfer nameservers to Vercel:
# NS → ns1.vercel-dns.com
# NS → ns2.vercel-dns.com
# Wait for DNS propagation (check with dig)
dig example.com A +short
# Should return 76.76.21.21
# SSL certificate auto-provisions after DNS verification
Step 6: Validate Feature Parity
# Compare old and new deployments
# Test all routes
for path in "/" "/about" "/api/health" "/api/users"; do
echo "=== $path ==="
echo "Old:"
curl -sI "https://old.example.com${path}" | head -3
echo "New:"
curl -sI "https://my-app.vercel.app${path}" | head -3
done
# Compare headers
diff <(curl -sI https://old.example.com/ | sort) \
<(curl -sI https://my-app.vercel.app/ | sort)
# Check redirects still work
curl -sI https://my-app.vercel.app/old-page | grep Location
Migration Checklist
Step
Validated
All functions converted to Vercel format
Required
Environment variables migrated with correct scoping
Required
Redirects and headers ported to vercel.json
Required
DNS configured and SSL provisioned
Required
Preview deployment tested end-to-end
Required
Performance baseline compared (old vs new)
Recommended
Monitoring and alerting configured
Required
Rollback plan documented (DNS revert)
Required
Old platform kept running during validation period
Recommended
Output
Configuration mapped from source platform to Vercel
Functions converted to Vercel serverless/edge format
Environment variables migrated with proper scoping
DNS cutover completed with SSL auto-provisioning
Feature parity validated
Error Handling
Error
Cause
Solution
Function format mismatch
AWS/Netlify handler signature
Convert to (req, res) or Web API format
Missing env var after migration
Not added to correct environment
Re-add with vercel env add
DNS not resolving
Propagation delay
Wait 24-48 hours, check with dig
SSL not provisioning
DNS records incorrect
Verify A/CNAME records match Vercel's requirements
