aid: kaiko:review
name: Kaiko Streaming Surface Review
kind: review
created: '2026-05-29'
modified: '2026-05-29'
reviewer: API Evangelist (Kin Lane)
subject: Kaiko Stream — real-time streaming protocols
sources:
  - https://docs.kaiko.com/stream/general/introduction.md
  - https://docs.kaiko.com/stream/general/quick-start-guides.md
  - https://docs.kaiko.com/stream/general/quick-start-guides/quick-start-python.md
  - https://docs.kaiko.com/stream/general/quick-start-guides/quick-start-curl.md
  - https://docs.kaiko.com/stream/data-feeds/introduction.md
  - https://github.com/kaikodata/kaiko-sdk-examples
  - https://sdk-documentation.kaiko.ovh
findings:
  - id: stream-transport
    summary: >-
      Kaiko Stream is delivered exclusively over gRPC streaming. The Kaiko Stream
      introduction explicitly states gRPC as the transport ("gRPC technology for the
      best data delivery and uptime"), the Python quick-start lists "gRPC streaming"
      as a system requirement, and the kaiko-sdk-examples repo describes Kaiko SDK as
      "leveraging gRPC Protocol and its capabilities." The SDK service protos
      (StreamTradesServiceV1, StreamAggregatedPriceServiceV1, StreamMarketUpdateServiceV1,
      etc.) are gRPC server-streaming Subscribe methods.
  - id: websocket-not-offered
    summary: >-
      No public Kaiko documentation page surfaced a WebSocket (ws:// or wss://) endpoint,
      subscription envelope, or channel definition for Kaiko Stream. There is no
      wss://stream.kaiko.com host documented. The previous apis.yml entry claiming a
      WebSocket transport with baseURL wss://stream.kaiko.com was inaccurate and has
      been corrected.
  - id: kafka-delivery
    summary: >-
      Kaiko also offers Cloud Delivery (S3, Snowflake direct shares) and Kafka-style
      managed delivery for some products, but those are out-of-band batch / managed
      pipelines, not a public WebSocket API.
  - id: rest-surface
    summary: >-
      Real-time-ish polling, historical data, reference data, indices, and on-chain
      data are exposed over the Kaiko REST API (us.market-api.kaiko.io / eu.market-api.kaiko.io)
      with X-Api-Key auth. REST is documented separately in openapi/kaiko-openapi.yml.
decision:
  asyncapi: false
  reason: >-
    Kaiko does not expose a documented WebSocket interface. Its real-time streaming
    surface is gRPC, which is out of scope for AsyncAPI 2.6 (AsyncAPI 2.6 has no
    first-class binding for gRPC server-streaming Subscribe RPCs the way it does for
    Kafka, MQTT, AMQP, or WebSocket). A gRPC contract is better expressed as the
    existing .proto files in github.com/kaikodata/kaiko-sdk. No asyncapi/kaiko-asyncapi.yml
    will be added at this time.
  followups:
    - Track Kaiko releases for any future WebSocket gateway (some vendors expose a
      WS bridge for browser clients) and revisit AsyncAPI then.
    - If Kaiko publishes a public Kafka delivery topology, evaluate an AsyncAPI 2.6
      spec with the kafka binding for the relevant topics.