Enabling High Concurrency
For isolation, from ACID properties:
- Typical: writers block readers, readers block writers
- But think about eBay
- Making a bid shouldn’t lock out page views
- Many page views shouldn’t lock out a bid
In many cases, people are happy with data that is consistent at a given point in time
Extreme example: sales rank of every book
- Ideally, want result as of some time (e.g., 8:00pm)
- Query may take a long time: don’t lock out sales