When migrating web hosting between providers while maintaining SSL encryption, a common challenge arises: can two independent certificates for the same domain coexist during transition? The answer is yes, and here's why this architecture works:

SSL certificates are bound to server configurations, not domain registrations. Each hosting environment maintains its own certificate store. Consider this Apache virtual host configuration example for the new server:

<VirtualHost *:443>
    ServerName domain.com
    SSLEngine on
    SSLCertificateFile /path/to/new/cert.pem
    SSLCertificateKeyFile /path/to/new/privkey.pem
    SSLCertificateChainFile /path/to/new/chain.pem
    # Other configuration directives
</VirtualHost>

The critical factor is DNS propagation timing, not certificate conflicts. When you update your domain's A record to point to HB's servers:

• Clients resolving to HA's IP will use HA's certificate
• Clients resolving to HB's IP will use HB's certificate
• No certificate revocation from HA is required

Modern CAs allow multiple valid certificates for the same domain. This is demonstrated by Let's Encrypt's rate limits:

# Let's Encrypt's weekly certificate issuance limits:
# 50 certificates per registered domain
# 5 duplicate certificates per week

1. Generate CSR on new server
2. Purchase/issue new certificate
3. Configure web server with new cert
4. Test via hosts file before DNS change
5. Update DNS TTL in advance (recommended 300s)
6. Cutover DNS records

If encountering SSL errors post-migration, verify:

openssl s_client -connect domain.com:443 -servername domain.com | openssl x509 -noout -dates

This confirms which certificate is being served and its validity period.

When migrating between hosting providers while maintaining the old environment temporarily, you may encounter this exact situation:

HostA (old provider) - certificate for example.com
HostB (new provider) - need to install new certificate for same example.com

From a technical standpoint, multiple valid SSL certificates can absolutely coexist for the same domain across different servers. The certificates themselves don't conflict because:

• SSL/TLS negotiation occurs independently per server
• Certificate Authorities don't enforce domain exclusivity
• The DNS system determines which server receives requests

The critical factor is DNS propagation when switching providers. Here's what happens during transition:

1. Both certificates remain valid during DNS propagation
2. Browsers will receive the appropriate certificate based on which IP the DNS resolves to
3. No certificate revocation is needed from the old provider

Here's how to safely execute the migration with Nginx as example:

# On new HostB server (Nginx config)
server {
    listen 443 ssl;
    server_name example.com;
    
    ssl_certificate /path/to/new/cert.pem;
    ssl_certificate_key /path/to/new/privkey.pem;
    # ... other SSL configurations
}

Watch out for these edge cases:

• Mixed content warnings if assets reference old URLs
• Certificate transparency logs showing both certificates
• CDN configurations that might cache the old certificate

Use these OpenSSL commands to verify both certificates:

# Check HostA's certificate
openssl s_client -connect hostA.example.com:443 -servername example.com | openssl x509 -noout -text

# Check HostB's certificate
openssl s_client -connect hostB.example.com:443 -servername example.com | openssl x509 -noout -text