Zero-downtime migration from GCP to Tencent Cloud

Feb 2023 – Feb 2026 Com2us Platform · Migration Role: Cloud Engineer · Main engineer

Moved 80 servers and 20 databases of Summoners War: Chronicles from GCP to Tencent Cloud in about one week with no downtime.

Scale: 80 servers · 20 databases

Overview

Problem

A live game had to move between clouds without stopping, and the firewall policy could not drift during the move.
Approach

Network and firewall rules were built on Tencent to match GCP first. Servers moved with the Online Migration tool and the same infrastructure was built. It then ran privately while the dev team checked for issues, and traffic moved in stages. The whole effort moved GCP Terraform code to Tencent Terraform code.
Result

The migration finished in about one week with no downtime. Some systems stayed on GCP while most game servers and databases moved to Tencent, and the firewall policy was fully reviewed and rebuilt along the way.
What I learned

The first step in moving between clouds was not moving servers but pairing the two clouds' resources by role. Mapping network, subnet, firewall, and server first made it simple to turn GCP Terraform code into Tencent Terraform code, and the firewall policy could be fully reviewed and rebuilt along the way. Avoiding downtime came from not switching everything at once: the same infrastructure was built first and run privately while issues were checked with the dev team, and traffic moved in stages. The infrastructure ended up as code, but I learned that the traffic cutover steps also need to live as code and a runbook for the next migration to repeat the same result.