Moving a live game between clouds without stopping it

The GCP infrastructure of Summoners War: Chronicles (80 servers, 20 databases) had to move to Tencent Cloud.

It was a live service, so downtime was not acceptable.

The biggest risk, I judged, was security policy going missing or being applied differently after the move.

Even with servers moved, a different firewall rule means the service fails, or something opens that should stay closed.

So I moved the network and firewall first, before the servers.

The whole process ran by converting GCP Terraform code into Tencent Terraform code, so the code records what changed and how.

Terraform resource mapping examples (representative resource names in each cloud)

The migration finished in about one week with zero downtime.

Because the migration lives in Terraform code, later operations and changes became easier.

The heart of multi-cloud operations is making the security standard move with you when you change clouds.

Moving between clouds firsthand gave me the instinct to account for each cloud’s different service structure in the migration design from the start.