Is one cache-file can be be shared between different smart-dns instances with different interfaces?

[GektorUA]

Subj, for example:

instance 1:
...
cache-file /tmp/smartdns.cache
server 8.8.8.8:53 -interface eth2
...

instance 2:
...
cache-file /tmp/smartdns.cache
server 8.8.8.8:53 -interface eth3
...

[PikuZheng]

To avoid dns pollution I recommend not to do this.

yes. it works for the same version, configuration group, and domain group.
the cache file is only read once at startup.