Scaling ChatGPT and scaling GitHub are very different problems.

For LLMs, prompt handling is effectively stateless. They do try to route follow-up prompts to the same cluster to benefit from prompt caching, but those can be effectively sharded. They also need to write results to storage but that's on a per-customer basis, so also easy to shard.

GitHub is a shared space, where commits and issues and PRs need to become instantly available to all readers across all geographies. They have a very different shape of scaling challenge to the LLM vendors.

Every response from GitHub must be deterministic. OpenAI and Anthropic do not have this problem.