BigData / Tableau Interview Questions
What is the difference between a live connection and an extract?
This choice determines whether Tableau talks directly to your source database on every interaction, or works off a locally stored snapshot.
| Live Connection | Extract |
| Every query hits the source database in real time. | Queries run against a local Hyper snapshot. |
| Data is always current, down to the second. | Data is only as current as the last refresh. |
| Performance depends entirely on the source system's speed. | Usually faster, since Hyper is optimized for analytical queries. |
| No extra storage or refresh scheduling needed. | Needs disk space and a refresh schedule. |
Live connections are the right call for operational dashboards that must reflect real-time data (like a live ops monitoring board), while extracts are usually preferred for reporting dashboards where slight staleness is acceptable in exchange for much better interactivity and query speed, especially against large or slow source systems.
Which connection type always reflects the very latest data in the source system?
Why might an analyst prefer an extract over a live connection for a large source table?
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