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Projector

The Projector service (app/projector/) builds the Valkey settings projection that consumer services (primarily Sesame) use for high-throughput reads.

Architecture

Section titled “Architecture”

Instead of having high-traffic consumer workers execute SQL queries against the various data services (Users, Modules, Commands), the Projector constructs flattened read-models.

  • Trigger: When a stream comes online (via ingress events), the Projector pre-warms the cache.
  • Cache Invalidation: Data services emit data.*.changed events and bagel.cache.invalidate.broadcaster when settings are updated. The Projector listens to these to rebuild the projection.
  • RPC Fallback: Services with cold local caches can call the Projector via NATS RPC to fetch the latest projection synchronously.

By isolating the read load into a dedicated projection in Valkey, the actual MySQL databases for configuration are shielded from the massive read volume generated by active Twitch chats.