OpenAI scaled Habitat, its online storage layer, to serve over 1 billion ChatGPT users by combining multi-tenancy architecture, global caching, and Azure Cosmos DB, achieving 12x faster read performance.
The engineering decisions behind that number are what make this worth reading. Multi-tenancy isolation prevented noisy-neighbor failures at scale. Global caching reduced redundant database hits across distributed regions. Cosmos DB handled the geo-replication without requiring OpenAI to build that infrastructure from scratch. Each choice compounds.
This is Part II, meaning the implementation details live here, not the theory. If you skipped Part I, the tradeoffs in tenant isolation and cache invalidation strategy documented in this piece stand on their own as a case study in scaling storage under real production load.
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