First Published At
First published at is the timestamp when a data record, such as a trade, quote, or OHLCV candle, first became available to users or systems.
In financial and cryptocurrency market data, first published at identifies the initial availability timestamp for a data record. It is different from the event time, exchange time, or period boundary associated with the record itself.
For example, a trade may occur at 10:00:01, be received by a data provider at 10:00:02, and first become available through an API at 10:00:03. In that case, the trade time describes when the market event happened, while first published at describes when users could first access it.
This distinction is important for historical replay, latency analysis, backtesting, audit trails, and data versioning. It helps users understand not only what happened in the market, but also when the information became observable to downstream systems.
Why First Published At Matters
First published at helps separate market event timing from data availability timing. This matters because trading systems, research pipelines, and compliance workflows often depend on knowing what information was available at a specific point in time.
Without first published at metadata, a historical dataset may appear cleaner or more complete than it was when originally consumed. That can introduce look-ahead bias in backtests or make it difficult to explain why two systems saw different data at the same moment.
For OHLCV candles and other derived datasets, first published at can also show when a provisional value first appeared before later correction, reconciliation, or backfill.
How is First Published At different from event time?
Event time describes when a market event occurred, such as when a trade was executed on an exchange. First published at describes when the record became available from a data source or API.
The two timestamps may be close together in real-time feeds, but they are not the same. Network delays, exchange publication delays, normalization pipelines, and validation steps can all cause availability to happen after the original event time.
How is First Published At used in backtesting?
In backtesting, first published at can help determine whether a strategy would realistically have had access to a data point at a given decision time.
If a historical record was first published after the simulated decision point, using that record in the strategy may create look-ahead bias. Tracking first published at helps make simulations more faithful to real-world data availability.
Why is First Published At important for corrected data?
When data is corrected or backfilled, first published at can distinguish the original publication time from later updates. This makes it possible to understand when a value first appeared and when it may have changed.
That distinction is useful for auditability, historical dataset versioning, and comparing different dataset vintages.
Real-World Example
Suppose a one-minute OHLCV candle covers the interval from 12:00:00 to 12:01:00. The candle is first published by an API at 12:01:02 with provisional values. At 12:01:20, a late-arriving trade is processed and the candle volume changes.
The first published at timestamp records when the candle first became available, while later update metadata can show when the corrected version was produced.
First Published At and CoinAPI Market Data API
CoinAPI Market Data API is designed to provide access to normalized cryptocurrency market data across exchanges. For users building backtests, analytics, trading infrastructure, or audit workflows, understanding publication timing helps separate market event time from data availability time.
Concepts such as first published at, availability time, correction windows, and dataset vintage are especially relevant when evaluating historical data quality, reproducibility, and time-sensitive decision logic.