Response Format & Freshness

The two envelope fields

Every successful JSON response carries two fields, added by the API rather than by each endpoint. endpoint_version identifies the deployment that produced the response. data_as_of reports when each upstream market-data feed last delivered to the node that answered you.

data_as_of is a fixed object: every key is present on every endpoint, and a key is null when that node has not received anything on that feed since it started.

{
  "symbol": "SPY",
  "underlying_price": 764.23,
  "as_of": "2026-08-25T18:49:00.697Z",
  "endpoint_version": "2026.08.25",
  "data_as_of": {
    "node": "fa2",
    "equity_feed": "2026-08-25T18:49:00.512Z",
    "equity_options_feed": "2026-08-25T18:48:58.204Z",
    "index_feed": null,
    "index_options_feed": null,
    "futures_feed": null,
    "futures_options_feed": null,
    "flow_feed": "2026-08-25T18:49:00.220Z",
    "oi_feed": "2026-08-21T20:00:00.000Z",
    "macro_feed": "2026-08-24T18:42:11.000Z"
  }
}

What each key reports

How to read it

• Check the feeds your query depends on. A GEX call on SPY is answered from equity_feed, equity_options_feed and oi_feed. futures_feed being null in that response says nothing about the answer.
• Compare against the cadence, not the clock. oi_feed at the previous session's close is correct - settled open interest is published once per session. In the example above it sits three days behind as_of because the request ran on a Monday and Friday was the last session to settle; that is right, not stale. equity_options_feed an hour behind during market hours, by contrast, is not.
• null means "not seen on this node", not "broken". A node that has never been asked for a futures symbol has never opened that feed.
• Spot and options are separate on purpose. They arrive over different pipes and can fail independently, so an index chain can be current while index spot is not.
• It reports feed activity, not per-contract freshness. A timestamp shows the feed delivered recently. It does not assert that every contract in a chain is equally current - an illiquid strike may not have quoted for hours while the feed itself is healthy.
• data_as_of is not as_of. as_of, where an endpoint returns it, is when the response was generated or when the newest contract in it last ticked. data_as_of describes the feeds behind it.

Arrays, Stock Summary and Historical

Endpoints that return a bare JSON array carry the same information in the X-Endpoint-Version and X-Data-As-Of response headers, the latter as compact JSON.

A call without an API key to Stock Summary returns a delayed snapshot and adds snapshot_as_of (captured_at, delayed: true).

On the Historical API, data_as_of means the same thing - live feed state - and every slot is null, because a historical node reads the archive rather than any live feed. The vintage of the archive rows replayed for your at is published alongside as archive_as_of, in the same shape.