A worked distinction
A response received now can contain a cached observation from an earlier request. Labelling every HTTP response as live hides this difference. A provider that does not return a snapshot timestamp cannot support a fabricated source time.
What to verify in your own analysis
Record provider, market, quote, source time when available, receive time and cache age. Reject incompatible or stale observations before combining venues; retries must not turn failures into invented prices.
Write down the market or protocol identifier, units, observation window and data source before comparing outputs. Keep unavailable values distinct from zero. Capture a baseline and change one assumption at a time so the resulting difference can be explained.
Use the linked working tools
Open the related tools below to inspect actual public observations or calculate a local scenario. The numerical example above is illustrative, not a current quote. Export the result together with its assumptions if you need a reproducible research record.
The review checklist records what you checked in this tab. Completion measures your own notes, not whether an investment is safe, suitable or profitable.