> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pg-sharding.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Fault Tolerance

The router stores the sharding rules only for cache purposes. Information about the entire installation is stored inside the QDB service, so the number of routers running simultaneously is unlimited.

In the router configuration, it is possible to specify multiple servers for one shard.