Historical data format is the same as provided by real-time Binance COIN Futures WebSocket API with addition of local timestamps. If you'd like to work with normalized data format instead (same format for each exchange) see downloadable CSV files or official client libs that perform data normalization client-side.
Tardis-machine is a locally runnable server that exposes API allowing efficiently requesting historical market data for whole time periods in contrast to HTTP API that provides data only in minute by minute slices.
depthSnapshot - generated channel with full order book snapshots
Binance COIN Futures real-time WebSocket API does not provide initial order book snapshots. To overcome this issue we fetch initial order book snapshots from REST API and store them together with the rest of the WebSocket messages - top 1000 levels. Such snapshot messages are marked with "stream":"<symbol>@depthSnapshot" and "generated":true fields.
During data collection integrity of order book incremental updates is being validated using sequence numbers provided by real-time feed (pu and u fields) - in case of detecting missed message WebSocket connection is being restarted. We also validate if initial book snapshot fetched from REST API overlaps with received depth messages.
Since Binance COIN Futures does not offer currently real-time WebSocket open interest channel, we simulate it by fetching that info from REST API (https://binance-docs.github.io/apidocs/delivery/en/#open-interest) every 30 seconds for each instrument. Such messages are marked with "stream":"<symbol>@openInterest" and "generated":true fields and data field has the same format as REST API response.