Thank you, @borkdude and @aviflax. I'll have a look at both.

Is it possible to relax requirements in s/keys? s/keys check input value with map? predicate. I try to spec datascript entity, but it implements only clojure.lang.Associative. https://github.com/tonsky/datascript/blob/master/src/datascript/impl/entity.cljc#L128 https://github.com/clojure/spec.alpha/blob/master/src/main/clojure/clojure/spec/alpha.clj#L857

entities are lazy. validating/conforming with s/keys would imply realizing and walking the entity graph (friends of friends of friends ...)