When game servers do not auto-scale and users receive many 503s and slow responses after a feature launch, what should you check first?

When game servers are not auto-scaling and users experience 503 errors and slow responses, the first thing to check is whether a Google Cloud project quota has been exceeded. Quotas limit resource consumption to prevent uncontrolled spending and resource exhaustion. If a quota, such as the maximum number of instances in an instance group or the rate of API calls for auto-scaling, is hit, new instances cannot be provisioned, leading to service degradation. While other options are potential issues, they are secondary. A database being offline would likely cause different error codes or complete service failure, not just slow responses and 503s on game servers. Performance bugs from a new feature are possible but less immediate than a hard quota limit preventing scaling. Load testing on production is a serious operational error, but a quota issue is a more fundamental infrastructure constraint to rule out first when auto-scaling fails.