The current release of clj-rethinkdb (0.15.26) depends on an alpha version of protobuf-java. This clashes with ClojureScript 1.9.854, which will not compile with this version. Adding an exclusion:
[com.apa512/rethinkdb "0.15.26" :exclusions [com.google.protobuf/protobuf-java]]
fixes the problem.
Are there reasons not to use protobuf-java 3.0.2? If not, it is perhaps worth making a release just with updated dependencies. While we're there, I'd also recommend updating the cheshire dependency.