Historical data format is the same as provided by real-time OKEx WebSocket v3 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 can 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.
Market data collection infrastructure for OKEx Swap since 2020-05-15 is located in GCP asia-northeast1 (Tokyo, Japan), before that it was located in GCP europe-west2 region (London, UK).
Real-time market data is captured via multiple WebSocket connections.
OKEx servers are located in Alibaba Cloud cn-hongkong region (Hong Kong, China).