# Performance and resiliency

For DNS resolvers, the most important parameter from performance perspective is cache hit rate, i.e. percentage of queries answered from resolver’s cache. Generally the higher cache hit rate the better.

Performance tunning should start with cache Sizing and Persistence.

It is also recommended to run Multiple instances (even on a single machine!) because it allows to utilize multiple CPU threads and increases overall resiliency.

Other features described in this section can be used for fine-tunning performance and resiliency of the resolver but generally have much smaller impact than cache settings and number of instances.

- Cache
- Multiple instances
- Prefetching records
- Cache prefilling
- Serve stale
- Root on loopback (RFC 7706)
- Priming module
- EDNS keepalive
- XDP for higher UDP performance