All terms
Glossary
Caching
Results are stored temporarily so that expensive computations or queries do not have to repeat.
Caches exist at every level: browser, edge, in front of the application, in front of the database. Each level has its own rules for validity and eviction.
The gain is response time and relief. The price is a second version of the truth that can drift from the first.
How you notice it
- The same expensive query runs a hundred times a minute.
- The database is the bottleneck under load.
- Content changes rarely but is read constantly.
Frequently asked
Time based or event based invalidation?
Time based, if data a few minutes old is acceptable, and it is more often than people assume. Event based only where freshness is mandatory, because it is the most common source of bugs that only appear in a particular order.