Concepts

Five concepts shape every Kairos analytic. Read them in order: the tick model and output stream define the wire-and-channel contract; the three contract pages justify the dispatch model, the historical surface, and the on-disk tick parquet schema.

Topic	Source of truth
TickEvent model	The variant set fed into every analytic.
OutputStream	Backpressure, lag policy, termination.
The dispatch model	Single-consumer dispatch contract — one consumer thread per ingest ring.
The historical surface	Bounded-termination historical contract — three-mode delivery (live / historical / replay).
The tick parquet schema	Tick parquet schema — one columnar RecordBatch per file.

Reading order

Recommended order for a new integrator:

1. TickEvent model — what flows in.
2. OutputStream — what flows out, and how the consumer drains it.
3. The dispatch model — why a single consumer thread, and what that buys.
4. The historical surface — why historical and replay share the same output type as live.
5. The tick parquet schema — what a recorded dataset looks like on disk.