Market data with the context left in.
Understand quote feeds, order books, listings, and market datasets through clear provenance, timestamps, units, and freshness policies.
Define what the record represents
A quote is an observation from a market source. A listing describes an asset being marketed. A statistic aggregates observations over a period. A command records an authorized instruction, and a result reports what a provider says happened. Keep these types separate even when they all contain prices or dates.
Preserve a minimum provenance envelope
Store the source identifier, provider record identifier, asset identity, units, currency where relevant, source time, receipt time, and freshness policy. For aggregated data, add geography, property or instrument type, measurement period, and definition. A single updated-at field cannot explain all of those dimensions.
Choose the appropriate transport
A streaming feed suits workflows that need repeated updates and have a documented recovery protocol. A REST lookup can suit individual records or periodic refreshes. A published dataset can suit historical and regional analysis. Select the transport from the question your product needs to answer, not from a belief that one protocol is always faster or more modern.
Make derived values reproducible
A spread, midpoint, depth total, or period comparison should retain its inputs and method. Use compatible observations and explicit rounding. Distinguish a calculation from a provider-reported field and mark assumptions in worked examples. Missing values should remain missing rather than silently becoming zero.
Separate observation from transaction permission
A user being permitted to view data does not establish authority to place an order, bid, or offer. Keep the data layer useful without execution and verify action permissions independently. The stock, crypto, and real-estate guides show how that distinction changes across sources.
Use source-specific documentation
Alpaca documents stock quote feeds; Coinbase documents venue-specific order-book channels; RESO describes standardized real-estate data exchange. Each route has its own semantics and access requirements. The official sources directory links to these primary references. Use the data-model example as an application-design aid rather than a replacement for their contracts.